Gemstones From Vietnam An Update

Huong G&G Fall 2012_Layout 1 9/28/12 4:29 PM Page 158
FEATURE ARTICLE
GEMSTONES FROM VIETNAM:

AN UPDATE
Le Thi-Thu Huong, Tobias Hger, Wolfgang Hofmeister, Christoph Hauzenberger, Dietmar Schwarz,
Pham Van Long, Ursula Wehmeister, Nguyen Ngoc Khoi, and Nguy Tuyet Nhung
This article describes the major gem materials of Vietnam, together with their new finds and recent pro-
duction. The gemological properties and chemical composition of ruby, sapphire, spinel, tourmaline,
garnet, and peridot from the most important Vietnamese sources are updated. Other gems such as aqua-
marine, green orthoclase, topaz, zircon, quartz, and pearls are briefly discussed. Commercially significant
deposits of ruby, blue and fancy sapphire, and spinel are located in two northern provinces: Yen Bai (Luc
Yen and Yen Binh Districts) and Nghe An (Quy Chau and Quy Hop Districts). Large volumes of blue,
green, and yellow sapphire come from the Central Highlands provinces of Dak Lak and Lam Dong, as
well as the southern provinces of Dong Nai and Binh Thuan. Of secondary commercial importance are
the tourmaline and garnet from Yen Bai and the peridot and zircon from the Central Highlands.
V
ietnam, with an area of 335,000 km2, occupies In March 1988, state-owned Vinagemco (Viet-
the eastern side of the Indochinese peninsula. namese Gems Company) was established to direct
Most of the countrys northern and central re- the exploration, mining, and trading of gem materials
gions are mountainous, reaching an elevation of (Kane et al., 1991; Pham et al., 2004b). Two sub-
3,142 m in the Fan Si Pan massif, near the Chinese sidiaries, Yen Bai Gemstone Company and Nghe An
border. The country is endowed with some 70 gem Gemstone Company, were set up in those provinces
deposits and 160 different occurrences (Nguyen et al., that same year. Ultimately, management problems
1995). Present gem production includes ruby, sap- led to the companys downfall in July 2003. Since
phire, spinel, tourmaline, peridot, garnet, aquama- then, no state-owned company has been active in the
rine, topaz, quartz, and green orthoclase (e.g., figure gem sector. Mining, processing, cutting, and trading
1). With more than 3,400 km of coastline, the coun- are all organized by private and joint-stock compa-
try is also a source of saltwater cultured pearls, and nies or private individuals.
several farms have emerged in recent decades. In ad- Scientific investigations of Vietnamese gem ma-
dition, Melo pearls are retrieved by fishermen on the terials, including their properties and the genesis of
southern coast and in Ha Long Bay in the north. the deposits, have resulted in several publications,
Compared with the countrys gem wealth, however, with special attention to ruby and sapphire (e.g.,
the Vietnamese mining industry remains undevel- Kane et al., 1991; Koivula and Kammerling, 1991;
oped. Although it has been nearly 30 years since col- Kammerling et al., 1994; Smith et al., 1995; Pham et
ored stones were discovered in Vietnam, mining and al., 2004a,b; Nguyen et al., 2011). This article updates
pearl farming activities are mostly small- and the occurrence, production, and gemological features
medium-scale operations run by private individuals of Vietnams major gem materials, and outlines the
or small companies. geology of the deposits.
GEOLOGY OF VIETNAM
See end of article for About the Authors and Acknowledgments.
GEMS & GEMOLOGY, Vol. 48, No. 3, pp. 158176,
Vietnam consists mainly of mountainous fold belts
http://dx.doi.org/10.5741/GEMS.48.3.158. surrounding the Yangtze and Indochina cratons (fig-
2012 Gemological Institute of America ure 2). The most important geologic event was the In-
158 GEMSTONES FROM VIETNAM: AN UPDATE GEMS & GEMOLOGY FALL 2012
Figure 1. Vietnam is a
contemporary source of
several gem varieties, in-
cluding ruby (center, 2.27
ct), spinel (left and bot-
tom stones, 1.975.07 ct),
aquamarine (second from
right, 3.48 ct) and green
orthoclase (top, 3.68 ct).
Courtesy of Palagems.com
and William Larson;
photo by Robert Weldon.
dosinian orogeny (Lepvrier et al., 2008) that occurred accumulated. Tertiary and Quaternary formations
in the Lower Triassic Period, 245240 million years were deposited in several graben and troughs, the
ago (Ma). This tectono-metamorphic episode gener- most important of which are located in the Cuu Long
ated northwest-trending dextral shear zones in central and Red River deltas. Plio-pleistocene tholeiitic
Vietnam, giving rise to the north-directed thrusting basalts (traps) form vast plateaus in southern Viet-
in northern Vietnam (Lepvrier et al., 2008). Later, sev- nam (Kunr, 2000).
eral extensional structures formed during the Meso- The formation of gems such as ruby, sapphire, and
zoic and the Cenozoic (e.g., the Hanoi and Cuu Long garnet along the Red and Chay Rivers was favored by
graben; see Kunr, 2000). During the subsequent metamorphic conditions that prevailed during the
India-Eurasia collision at around 50 Ma, the lateral Cenozoic. The tectonic setting, marked by vertical
displacement of Indochina produced major strike-slip shearing, allowed the circulation of fluids and the for-
shearing along the Red River and the opening of the mation of ore deposits. In Luc Yen, the Tertiary age
East Vietnamese Sea (Tapponnier et al., 1990; Leloup of ruby formation clearly matches that of the shear-
et al., 2001). Left-lateral shearing along the Red River ing movements, as shown by Ar/Ar and U/Pb dating
occurred later, after 21 Ma, and was apparently unre- on mica and zircon, respectively (Garnier et al.,
lated to the India-Asia collision (Searle, 2006). 2005a, 2006). The same Tertiary age of ruby forma-
Vietnam is formed by various rocks of Precam- tion is recorded in the Quy Chau area along the
brian to Quaternary age. Although the old Precam- northern border of the Bu Khang Massif, where the
brian basement was generally reworked during the shearing was manifested as a north-dipping, low-
Indosinian Orogeny, isotopic dating has revealed the angle shear zone, in an extensional context (Jolivet
existence of a protolith of at least Proterozoic age in et al., 1999).
the Kontum Massif of central Vietnam. The age of According to Nguyen and Flower (1998), sapphire
the metamorphic rocks related to ruby, sapphire, and and zircon from the Central Highlands were em-
garnet along the Chay and Red Rivers is essentially placed as xenocrysts in Quaternary basalts that
Tertiary, but this metamorphism is superimposed formed as a result of mantle plume activity. Two dis-
over earlier events (Searle, 2006). Paleozoic forma- tinct basalt suites are recognized in the area: tholei-
tions are widespread, comprising Cambrian series, itic (without any xenocrysts) and alkaline (containing
thick Silurian formations (including schists and mantle and lower crustal xenocrysts, including
sandstones), and Devonian and Permo-Carboniferous gems). The U/Pb dating of zircon recovered from the
limestones that form vast areas of northern Vietnam. basaltic placers suggests two eruptional events, at
Basalts related to Permian mantle plume activity ~6.5 and ~1 Ma (Garnier et al., 2005b).
occur along the Da fault. Lower Triassic series are
mainly terrigenous, whereas the middle Triassic con- MATERIALS AND METHODS
sists of limestones and volcanic rocks (Tran et al., Most of the samples used for this study were pur-
2008). In the troughs formed during the Jurassic and chased or collected by the authors at the mines from
Cretaceous, thick continental series and volcanics 2009 to 2012. Among these were 339 corundum sam-
GEMSTONES FROM VIETNAM: AN UPDATE GEMS & GEMOLOGY FALL 2012 159
Gem Mining Areas

1 Yen Bai: Topaz, green orthoclase, tourmaline,
Yangtze craton
garnet, spinel, ruby, sapphire
2 Phu Tho: Quartz, topaz, aquamarine, garnet

China 3 Thanh Hoa: Quartz, topaz, aquamarine, garnet
4 Nghe An: Quartz, aquamarine, garnet, spinel,
1 ruby, sapphire
2 Hanoi 5 Quang Nam: Ruby, sapphire
Ha Long 6 Da Nang: Rose quartz

7 Kon Tum: Zircon, garnet
8 Gia Lai: Zircon, amethyst, peridot
Thanh Hoa 9 Dak Lak: Zircon, peridot, sapphire

3
Hainan 10 Dak Nong: Zircon, sapphire
4
Island 11 Khanh Hoa: Citrine
Vinh 12 Lam Dong: Zircon, smoky quartz, topaz,
peridot, sapphire
13 Binh Thuan: Zircon, sapphire
La
14 Dong Nai: Sapphire

os
Key
Rivers
Da Nang
5
6 Faults
Indochina craton Basalts
7 Granite massif
Kon Tum massif

8
9 Indosinian folding
10 Nha
Trang Cenozoic troughs
11
12 Mesozoic troughs
13
Cam Ranh
14 Paleozoic troughs
Phan Thiet
Proterozoic folding
Ho Chi Minh City
Phu Quoc Cuu Long Proterozoic troughs
Island Delta
N
0 200 km
Figure 2. This map shows Vietnams 14 most important gem provinces and the major geologic environments.
Modified after Kunr (2000) and Lepvrier et al. (2008).
ples, including 143 rough and 196 polished stones lands and southern provinces. While corundum was
(112 faceted and 84 cabochons) ranging from 0.6 to discovered almost three decades ago in the north,
6.3 ct. We examined 85 faceted spinels and 33 spinel Vietnamese geologists did not find the gems in the
crystals (1.84.7 ct) of various colors. The 76 tourma- central and southern provinces until the early 2000s.
lines (2.418.5 ct) consisted of 20 faceted samples, 10 Among these localities, Yen Bai remains the most
cabochons, and 46 crystals in a variety of colors. We important source of ruby and fancy sapphire,
examined 16 faceted garnets (1.54.2 ct) and 15 gar- whereas central Vietnam is the main supplier of blue
net crystals (2.86.6 ct), plus 26 faceted and 17 rough to dark blue sapphire.
peridot (3.26.2 ct). The remaining samples consisted The older mines in Yen Bai have been exploited
of green feldspar: one faceted stone and two cabo- since before the mid-1990s, and many of them have
chons (7.88.5 ct), as well as two crystals. Gemolog- been abandoned. All the old mines (including Nuoc
ical properties of the samples were established using Ngap, Hin Om, Khau Nghien, Vang Sao, May
a dichroscope, Schneider refractometer, hydrostatic Thuong, May Ha, Phai Chap, Tan Lap, and Lam
Shimadzu balance, UV lamp, and Schneider immer- Dong) are located in Luc Yen District, mainly near
sion microscope with Zeiss optics. Khoan Thong and An Phu along the east side of the
Electron microprobe analyses of the spinel, tourma- Chay River. The newer mines in Yen Bai (opened
line, peridot, and garnet samples were performed with since the mid-1990s) are situated on the west side of
a JEOL JXA 8900RL instrument equipped with wave- the Chay River. These include the Lang Chap and
length-dispersive spectrometers, using 20 kV acceler- Truc Lau areas of Luc Yen District and the Tan Dong,
ation voltage and 20 nA filament current. The Hoa Cuong, and Tan Huong areas of the neighboring
measurements were calibrated with natural minerals Yen Binh District to the southeast (see Nguyen et al.,
and synthetic compound standards. The light elements 2011, for a map of the Luc Yen mining area).
B and Li were analyzed in the tourmaline samples Perhaps the most influential company in Viet-
using an Agilent 7500ce ICP-MS in pulse-counting nams gem industry today is the DOJI Gold & Gems
mode, and ablation was achieved with a New Wave Group, which now works a ruby and sapphire mine
Research UP-213 Nd:YAG laser ablation system, in Truc Lauthe only deposit being exploited on a
using a pulse repetition rate of 10 Hz, an ablation time large scale. Current production from this deposit to-
of 60 seconds, a dwell time of 10 milliseconds per iso- tals around 10 kg per month, consisting of 2030%
tope, a 100 m crater diameter, and an average of five ruby (and some sapphire) and 7080% spinel. Only
laser spots for each sample. NIST SRM 612 glass was 1015% of the total production is of cabochon qual-
used as an external calibration standard. ity; the rest is used for carvings or specimens
Raman spectra of four feldspar samples were col- (Nguyen et al., 2011). An 18.8 kg star ruby of good
lected with a Jobin Yvon LabRam HR 800 spectrome- quality, discovered by DOJI in the Tan Huong mine
ter coupled with an Olympus BX41 optical microscope in 2005, is the largest known Vietnamese ruby spec-
and an Si-based CCD (charge-coupled device) detector; imen (see Nguyen et al., 2011).
samples were excited by a 514 nm green Ar+ ion laser. Ruby and sapphire mining in other areas of the
Raman microscopy of inclusions in spinel, tourmaline, country is sporadic and small scale, and recent overall
peridot, and garnet samples was performed in confocal production is significantly lower than during the peak
mode, facilitating analysis at the micron scale (25 years of the 1990s. The deposits are situated mostly
m). in remote areas in the mountains and jungles. They
Powder X-ray diffraction analysis was performed require large-scale operation but have only been
on a portion of one green feldspar sample with a worked by local people equipped with primitive tools.
Seifert XRD 3000 TT diffractometer using CuK ra- According to Mr. Duong Anh Tuan, vice general di-
diation (40 kV and 30 mA). rector of the DOJI Group, the country as a whole ex-
ported approximately 2 tonnes of gem-quality ruby
RUBY AND SAPPHIRE and sapphire rough in 2010 and 1.5 tonnes in 2011.
Ruby and several colors of sapphire are found in Yen Hauzenberger et al. (2003) noted four types of pri-
Bai Province in the north and in Nghe An and Quang mary gem corundum deposits in Vietnam:
Nam Provinces in central Vietnam. Sapphire also oc- 1. Ruby and sapphire associated with metaso-
curs in the provinces of Lam Dong, Dak Nong, Dak matic-metamorphic processes in high-grade
Lak, Binh Thuan, and Dong Nai in the Central High- rocks: the Co Man outcrop at Truc Lau Valley,
TABLE 1. Gemological characteristics of ruby and sapphire from Luc Yen, Vietnam.a
Khoan ThongAn Phu, Yen Bai (old mines)b Tan HuongTruc Lau, Yen Bai (new mines)c
Property No. samples Observations No. samples Observations
(this study) (this study)
Color 118 rough and Colorless, gray, pink, purplish pink, 73 rough and Colorless, orange, gray (to yellowish
polished medium to dark red, light to dark blue polished grayc), pink, medium to dark red, orangy
red, light to dark blue
Moderate to highly saturated purplish
red to purplish pink through reddish Bluish or greenish gray, pink, pinkish to
purple to pinkish purple in medium purplish and brownish redc
light to dark stonesb
Diaphaneity 118 rough and Opaque to translucent, semitransparent 73 rough and Poor to moderate clarity, opaque to
polished to transparent polished translucent, semitransparent to transparent
Refractive indices 35 faceted no = 1.7601.763, ne = 1.7681.771 20 faceted no = 1.7611.763, ne = 1.7691.772
no = 1.7591.762, ne = 1.7681.770b no = 1.7621.763, ne = 1.7701.771c
10 cabochon n = 1.761.77 (spot method)
Birefringence 35 faceted 0.0080.009 20 faceted 0.0080.009
Optical character 35 faceted Uniaxial negative 20 faceted Uniaxial negative
Specific gravity 85 polished 3.924.04 30 polished 3.914.02
3.924.00b 3.914.07c
Pleochroism 25 cabochon Moderate to strong dichroism 30 polished Moderate to strong dichroism
Weak to strong dichroismc
UV fluorescence
Long-wave 25 cabochon Pink to red: Weak to strong red (to 30 polished Pink to red: Weak to strong red
orangy redb)
Gray and colorless: Orange (inertc)
Gray and colorless: Orange
Light to dark blue: Light blue, orange
Light to dark blue: Light blue, orange
Orange: Strong orange-red
Short-wave 25 cabochon Pink to red: Weak to strong red 30 polished Pink to red: Weak to strong red
Gray and colorless: Orange Gray and colorless: Orange (inertc)
Light to dark blue: Light blue, orange Light to dark blue: Light blue, orange
Orange: Orange-red
Internal features 50 polished Apatite, rutile (needles, clouds), 30 polished Rutile (needles, silk, clouds, and stringer
ilmenite, zircon, biotite, muscovite, formations), ilmenite, zircon, apatite,
diaspore, boehmite, calcite, amphibole, spinel, diaspore, plagioclase, biotite,
hematite, tourmaline, chlorite, spinel, muscovite, chlorite, magnetite, hematite
kaolinite, pargasite
Growth zoning, parting, lamellar
Nordstrandite, pyrrhotite, phlogopiteb twinning, fractures
Swirled growth featuresb, blue color Liquid-gas inclusions
zones, lamellar twining, fractures
Liquid-gas inclusions
a
Properties as obtained in this study, unless otherwise noted.
b
Kane et al. (1991).
c
Nguyen et al. (2011).
the Khe Nhan and Kinh La occurrences in the 3. Sapphire related to basaltic rocks: Dak Lak and
Tan Huong area, and the Phuoc Hiep mining Lam Dong in the Central Highland provinces,
area in Quang Nam Province. and Dong Nai and Binh Thuan in the southern
2. Ruby and fancy sapphire from marble: Yen Bai provinces.
Province (Khoan Thong, An Phu, Nuoc Ngap, 4. Ruby from pegmatite-like rocks in feldspathic
Hin Om, Khau Nghien, Vang Sao, May Thuong, matrix: occurrences near kilometer markers 12,
May Ha, Phai Hap, Tan Lap, Lam Dong, Slope 15, and 23 along National Road 70 in the Luc
700 outcrop in Bao Ai ward, Tan Huong drill Yen and Yen Binh areas of Yen Bai Province.
core, and DOJIs Truc Lau mine) and Nghe An Today, however, ruby and sapphire are primarily
Province (Quy ChauQuy Hop). mined from secondary deposits.
Figure 3. Ruby and sap-

phire from Luc Yen are
typically of cabochon
quality, and some show
asterism. The samples on
the left are 3.65.3 ct; the
pair on the right weigh
3.8 and 4.7 ct. Photos by
Pham Van Long.
Description of the Material. Several authors (Bank greenish or yellowish hues. Vietnams finest blue
and Henn, 1990; Kane et al., 1991; Koivula and Kam- sapphires (e.g., figure 4) come from a metamorphic
merling, 1991) have concluded that the characteris- deposit at Nghe An. Compared to ruby and sapphire
tics of rubies from Luc Yen (the older mines) and Quy from Yen Bai and Nghe An, the material from Quang
Chau are generally comparable with stones from Nam is of lower quality and transparency. It also
Mogok, Myanmar. The gemological properties of typically contains lower concentrations of coloring
ruby and sapphire from the old and new mines of Luc elements (Cr, Fe, and Ti) than material from else-
Yen are summarized in table 1. Rubies from these where (Nguyen et al., 2007). According to local deal-
two Vietnamese sources can be differentiated by ers, these gems have been traded mostly in the
their ratios of Cr2O3/Fe2O3 and Cr2O3/TiO3, both of domestic market.
which are higher in Luc Yen samples (Hauzenberger
et al., 2003). A comparative study of the Yen Bai ma- SPINEL
terial by one of the authors (Nguyen et al., 2011) in- Vietnamese spinel was initially discovered at Luc
dicated lower Cr and higher Fe in ruby from the Yen (Yen Bai Province) and Quy Chau (Nghe An), at
newer mines. Furthermore, distinctive internal fea- the same time as the ruby and sapphire finds. Today,
tures in ruby and fancy sapphire from the old mines Yen Bai is the only active source. The major deposits
were presented by Kane et al. (1991). Supplies of are located at An Phu, Khoan Thong, Minh Tien, and
facet-grade ruby from Luc Yen (as well as Quy Chau) Truc Lau in Luc Yen, and at Tan Huong in Yen Binh.
have become rare, and cabochon-quality ruby and The newest deposit, found in February 2010, is Lang
fancy sapphire are more common (figure 3). Chap, notable for its orange-red padparadscha-like
One interesting feature of ruby and sapphire from stones (Nguyen et al., 2011). Yet the most productive
the newer mines is that the crystals are very typically spinel deposit remains the old Cong Troi mine in An
surrounded by spinel, which generally follows the Phu, which yields a wide range of colors (Blauwet,
morphology of the underlying corundum crystal (see 2010). According to local dealers in Luc Yen, since
Nguyen et al., 2011). The boundary between the
corundum and the spinel is slightly rounded, suggest-
Figure 4. The highest-quality Vietnamese sapphires
ing disequilibrium between the two (Hger et al.,
are found in Nghe An Province (Quy ChauQuy
2010; Hauzenberger et al., 2010). The formation of
Hop). These examples weigh 4.35.2 ct. Photo by
this spinel is explained by the reaction: Le Thi-Thu Huong.
Al2O3 + CaMg(CO3)2 Al2MgO4 + CaCO3 + CO2
Corundum + Dolomite Spinel + Calcite + CO2
The gem properties of gem corundum from Nghe
An (Quy ChauQuy Hop), Quang Nam, and the
Central Highlands and southern provinces are sum-
marized in table 2. Most of the sapphires from cen-
tral and southern Vietnam are associated with
basalts, and are notable for their high Fe content.
They are generally dark blue, though some have
Figure 5. In Luc Yen,

pure white marble typi-
cally hosts red spinel
(left, largest crystal is
2.5 cm wide), while a
more complex marble
assemblage hosts spinel
of other colors (right,
crystal is 4.0 cm wide).
Photo by Pham Van
Long.
the beginning of 2012 Yen Bai has produced roughly from the complex marbles are thought to be meta-
200 kg of spinel monthly (excluding the production somatic (Hofmeister, 2001).
from DOJIs Truc Lau mine).
There are two different geologic origins of gem Description of the Material. Besides their wide range
spinel in Luc Yen. The more intense red spinel typ- of colors, including pink to red, orange-red, reddish
ically comes from calcitic to dolomitic marble (e.g., brown, violet, purple, cobalt blue, and light to dark (fig-
ure 6), some Vietnamese spinels exhibit a color change.
In these specimens, the violetish blue color seen in flu-
orescent light changes to violet-purple under incandes-
In Brief
Vietnam is a source of ruby, sapphire, spinel, tourma-
line, peridot, garnet, aquamarine, green orthoclase, Figure 6. These faceted Vietnamese spinels from Luc
topaz, zircon, quartz, and pearls (cultured saltwater Yen (1.83.2 ct) exhibit a wide range of color. Photo
and freshwater, as well as natural Melo). by Le Thi-Thu Huong.
Updated gemological data is provided for ruby, sap-
phire, spinel, tourmaline, peridot, and garnet, and new
chemical data is presented for spinel, tourmaline,
peridot, and garnet.
The most important Vietnamese gem localities consist
of the marble-hosted ruby, sapphire, and spinel de-
posits in Yen Bai and Nghe An Provinces.
figure 5, left), sometimes associated with clinochlore

or phlogopite. In contrast, violet, purple, brown, and
blue spinels are found in marble with a more com-
plex mineral assemblage containing clinohumite,
pargasite, clinochlore, and forsterite (e.g., figure 5,
right). The red spinels from the more pure marbles
have a similar formation environment as marble-
hosted rubies (i.e., metamorphic), while the spinels
TABLE 2. Gemological characteristics of gem corundum from other localities in Vietnam.
Ruby and sapphire from Nghe An Ruby and sapphire from Sapphire from Central Highlands
(Quy ChauQuy Hop)a Quang Namb and southern provincesc
Property No. samples Observations No. samples Observations No. samples Observations
(this study) (this study) (this study)
Color 37 rough Pink, purplish pink to 35 rough Colorless, gray, purplish 76 rough Yellowish light blue,
and polished red, light to dark blue and polished pink to red, grayish blue and polished greenish, green
yellowish to dark blue
Moderate to highly Violetish pink, brownish
saturated purplish red to redc Weak to highly
purplish pink through saturated colors ranging
reddish purple to pinkish from blue to bluish
purple in medium light green, with tones from
to dark stonesb light to extremely darkd
Diaphaneity 37 rough Poor to moderate 35 rough Opaque to translucent 76 rough Opaque, translucent,
and polished clarity, translucent, and polished and polished semitransparent to
semitransparent to transparent
transparent
Most are slightly to
moderately includedd
Refractive 14 faceted no = 1.7591.762, 3 faceted no = 1.7601.761, 40 faceted no = 1.7611.765,
indices ne = 1.7671.771 ne = 1.7681.771 ne = 1.7701.775
no = 1.7591.762, no = 1.7601.766, no = 1.7601.764,
ne = 1.7681.770b ne = 1.7681.774c ne = 1.7691.772d
Birefringence 14 faceted 0.0080.009 3 faceted 0.0080.010 40 faceted 0.0080.010
Optical 14 faceted Uniaxial negative 3 faceted Uniaxial negative 40 faceted Uniaxial negative
character
Specific 18 polished 3.984.04 11 polished 3.914.03 52 polished 3.964.05
gravity
3.924.00b 3.904.03c 3.994.02d
Pleochroism 18 polished Moderate to strong 11 polished Moderate (to strongc) 52 polished Greenish blue, yellowish
dichroism dichroism green dichroism
Strong dichroism: blue
to violetish blue parallel
to the c-axis and mostly
green-blue to yellow-
green perpendicular to
the c-axisd
UV fluorescence
Long-wave 18 polished Pink to red: Weak to 11 polished Pink to red: Inert 20 polished Inert
strong red (to orangy redb)
Gray and colorless: Inert
Light to dark blue: Light
blue, orange
blue
Short-wave 18 polished Pink to red: Weak to 11 polished Pink to red: Inert 20 polished Inert
strong red (to orangy redb)
Gray and colorless: Inert
blue, orange
blue
Internal 18 polished Amphibole, boehmite, 11 polished Garnet, mica, chlorite 52 polished Uranpyrochlored,
features calcite, diaspore, mus- plagioclase, boehmite,
Color zoning, twinning
covite, biotite, graphite, columbite, zircon,
kaolinite, rutile, zircon ilmenite, pyrrhotite,
spinel, goethite, kaolinite
Calcite, apatite,
nordstrandite, Color zoning, growth
pyrrhotite, phlogopiteb structures, laminated
twinning, fine-grained
Blue color zonesb, color
clouds, needle-like
zoning, liquid-gas
inclusions, fingerprints,
inclusions
negative crystals
a
Properties as obtained in this study, unless otherwise noted.
b
Kane et al. (1991).
c
Nguyen et al. (2007).
d
Smith et al. (1991).
TABLE 3. Gemological characteristics of spinel from Luc Yen, Vietnam.
Property No. samples Observations Data from the literature
Color 118 rough and Pink to red, orange-red, reddish brown, violet, Orangy red to purple, orangy pink to purplish
faceted purple, light to dark and cobalt blue; some pink, violet to blue (Koivula et al., 1993),
exhibit a color change padparadscha-like (Blauwet, 2011), cobalt-blue
(Blauwet, 2011; Smith et al., 2008)
Diaphaneity 114 rough and Semitransparent to transparent nr a

polished
Refractive indices 85 faceted 1.7121.719 1.7141.719 (Koivula et al., 1993)
1.7121.718 (Smith et al., 2008)
Specific gravity 85 faceted 3.583.73 3.593.63 (Koivula et al., 1993)
3.543.71 (Smith et al., 2008)
UV fluorescence
Long-wave 25 faceted Pink to red: Red Pink to red: Weak to moderate red
Brown, violet, blue: Inert Purple to blue: Weak or inert (Koivula et al., 1993)
Short-wave 25 faceted Pink to red: Red Similar in color but of lesser intensity (Koivula et
al., 1993)
Brown, violet, blue: Inert
Internal features 85 faceted Apatite, hgbomite, hematite, goethite, rutile, Muscovite, apatite, zircon, graphite, hgbomite,
K-feldspar, pyrite hematite, goethite
Fingerprints, primary liquid-gas inclusions, Rutile silk, decorated intergrowths, ribbon-like
negative crystals stepped growth planes (Koivula et al., 1993;
Gbelin and Koivula, 2008)
a
Abbreviation: nr = not reported.
cent light, or the light blue color changes to light laven- Yen (see G&G Data Depository at gia.edu/gandg) gave
der (Senoble, 2010; Blauwet, 2011a). See table 3 for the various concentrations of chromophores (V, Mn, Ti, Cr,
gemological properties of Luc Yen spinel, and figure 7 Fe, and Co). Red spinel contained the greatest
for some common inclusions. chromium contents (up to 1.19 wt.% Cr2O3). Vana-
Chemical analyses of our spinel samples from Luc dium was highest in red-orange spinel (0.61 wt.%). Pur-
Figure 7. Luc Yen spinel

may show parallel lay-
ers of fingerprints
(A), as well as inclu- A B
sions of K-feldspar (B),
rutile (C), and apatite
(D). Photomicrographs
by Le Thi-Thu Huong;
magnified 35.
C D
Figure 8. The principal

colors of Luc Yen tour-
maline are pink, green,
brown, and yellow. The
crystals range up to 2.7
cm long, and the cut
samples weigh up to 5.1
ct. Photos by Nguyen
Duc Trung Kien.
ple and dark blue samples had the greatest iron con- Wilson, 2007; Nguy et al., 2010). The Luc Yen area
tents, with up to 1.84 wt.% FeO, though the purple produces approximately 200 kg of tourmaline annu-
spinel had higher Cr and Ti. Dark cobalt-blue material ally, which is lower than its output of ruby, sapphire,
had only a small amount of cobalt (0.09 wt.% CoO), and spinel. Nevertheless, the quality and variety of
but also contained 0.71 wt.% FeO, 0.23 wt.% NiO, and colors make tourmaline one of the most important
0.14 wt.% Cr2O3. Therefore, each particular color in gems from the area.
spinel is attributable not to any one element but rather
a combination of elements. Further study is required Description of the Material. The crystals consist of
to explain the exact causes of color in these spinels. typical striated prisms with rounded triangular cross
sections and various terminations. The principal col-
TOURMALINE ors of tourmaline, whether from primary or secondary
To date, Luc Yen is Vietnams only known source of deposits, are pink, green, brown, and yellow (figure 8).
gem tourmaline. Along with spinel, tourmaline was Multicolored crystals usually display alternating
first discovered in alluvial gravels, mainly at Khoan pink/green and brown/yellow colors. Color zoning is
Thong, An Phu, and Minh Tien. Pegmatite-hosted, often observed from the center to the periphery of the
non-gem-quality tourmaline was probably found in crystals, with a combination of pink/dark green (Pham
the Luc Yen area during the early 2000s. Yet gem-qual- et al., 2004a) or yellowish green/red (Laurs et al., 2002).
ity stones have only been mined since 2004 at Minh See table 4 for gemological properties, and figure 9 for
Tien and since 2009 at Khai Trung (Blauwet, 2007; examples of some inclusions in Luc Yen tourmaline.
Figure 9. Tourmaline from Luc

Yen contains abundant fluid in-
clusions (A and B), as well as
crystals of apatite (C), diopside
(D), and quartz (E). Photomicro-
graphs by Le Thi-Thu Huong;
magnified 35.
A B
C D E
Chemical analyses of our samples showed that

they all were elbaite (table 5). Studies by Laurs et al.
(2002) and Wilson (2007) also identified rossmanite
and liddicoatite from Luc Yen.
Figure 10. These Vietnamese peridot gemstones range
PERIDOT from 5.7 to 6.2 ct. Photo by Nguyen Duc Trung Kien.
Peridot was discovered in Vietnam in the early 1990s
(Koivula et al., 1993). Gem-quality peridot has been
obtained from three provinces in the Central High- (Phu Tho Province), Thuong Xuan (Thanh Hoa), and
lands: Gia Lai, Dak Lak, and Lam Dong. Of these, Ky Son (Nghe An). Pyrope-almandine also occurs
Gia Lai is the most important source. Two deposits with olivine, phlogopite, and perovskite in some
there, Ham Rong and Bien Ho, yield about 100 kg kimberlite dikes in Kon Tum Province in the Central
monthly, with 1520% being gem quality. Including Highlands. In Luc Yen, where garnet production
the output from the two other provinces, Vietnam could reach 5060 kg annually, almandine-pyrope is
could produce up to several hundred kilograms of found as an accessory gem mineral with other stones
gem peridot annually. such as ruby, sapphire, and spinel in placer deposits.
Vietnamese peridot occurs in lherzolite xenoliths The output from Kon Tum and other localities is un-
within basalt flows. The gem has been extracted mostly known.
from alluvial gravels. In some places, miners must dig
pits 5 m deep to reach the peridot-bearing layers. Description of the Material. Vietnamese garnets have
a brownish red color and yield cut stones ranging
Description of the Material. Most Vietnamese peridot from 1.5 to 4.5 ct (e.g., figure 12). See table 8 for their
occurs as pebbles averaging 0.6 to 1.5 cm in diameter. gemological properties, and figure 13 for some typical
Pieces as large as 4 cm in diameter are occasionally inclusions.
found. Faceted stones show an attractive yellowish Chemical analyses revealed that the Luc Yen and
green color (figure 10). See table 6 for the gemological Kon Tum garnets are composed mainly of alman-
properties of Vietnamese peridot, and figure 11 for dine-pyrope solid solutions. The composition of Luc
some common inclusions. No systematic differences Yen garnet consists of approximately 83% alman-
were noted in the gemological characteristics or dine, 13% pyrope, 3% grossular, and 1% spessartine.
chemical composition (table 7) of Vietnamese peridot Kon Tum garnet contains 63% pyrope, 33% alman-
from the three provinces. The samples all consisted dine, 3% grossular, and 1% spessartine (table 9).
of 91% forsterite and 9% fayalite, with trace amounts
of Ni, Cr, Mn, and Ca. OTHER GEMS
Aquamarine and Irradiated Beryl. Aquamarine is
GARNET known from northern Vietnam at Thuong Xuan
Gem-quality garnet (almandine and pyrope) occurs (Thanh Hoa Province), Que Phong (Nghe An), and
in the Luc Yen area and in smaller amounts else- Thach Khoan (Phu Tho), and has been described in
where in northern Vietnam, including Thach Khoan several references (Pham et al., 2004a; Laurs, 2010;
Figure 11. Vietnamese

peridot may contain
inclusions of spinel
(left, with an associ-
ated discoid fracture)
or sphalerite (right).
Photomicrographs by
Le Thi-Thu Huong;
magnified 35.
TABLE 4. Gemological characteristics of tourmaline from Luc Yen, Vietnam.
Property No. samples Observations Data from the literature
Color 76 rough and Pink, yellow, green, reddish brown Pink, raspberry red to yellow-green and
polished yellow-orange (Wilson, 2007; Laurs et al., 2002)
Diaphaneity 76 rough and Semitransparent to transparent
polished
Refractive 20 faceted Pink: no = 1.6381.639 Pink: no = 1.641, ne = 1.623
indices ne = 1.6191.621
Yellowish green: no = 1.640, ne = 1.620
Yellow: no = 1.6421.646
Red: no = 1.647, ne = 1.625
ne = 1.6251.628
(Obtained from a color-zoned sample; Laurs et
Green: no = 1.6351640
al., 2002)
ne = 1.6211.625
Reddish brown: no = 1.6381.644
ne = 1.6241.626
Birefringence 20 faceted Pink: 0.0180.019 Pink: 0.018
Yellow: 0.0170.018 Yellowish green: 0.020
Green: 0.0170.019 Red: 0.022
Reddish brown: 0.0160.020 (Obtained from a color-zoned sample; Laurs et
al., 2002)
Optical 20 faceted Uniaxial negative nr a
character
Specific 28 polished Pink: 3.053.08 nr
gravity
Yellow: 3.173.19
Green: 3.173.20
Reddish brown: 3.063.08
Pleochroism 28 polished Pink: Light pink to pink nr
Yellow: Yellowish to yellow
Green: Yellowish green to green
Reddish brown: Greenish yellow to brownish
green
UV fluorescence
Long-wave 28 polished Inert (in all colors) Pink to red: Inert
Yellowish green: Weak yellow-green
Short-wave 28 polished Inert (in all colors) Pink to red: Inert
Yellowish green: Inert (Laurs et al., 2002)
Internal features 28 polished Apatite, quartz and diopside Healed fractures, color zoning, unknown solid
inclusions (Laurs et al., 2002)
Growth tubes, color zoning
Liquid-gas inclusions
Planar fluid inclusions
a
Shigley et al., 2010; Blauwet, 2011b; Le et al., 2011). ing to local dealers, production from this area alone
The Thuong Xuan mining area, located 170 km was 300400 kg in 2010 and about 500 kg in 2011.
southeast of Hanoi, is the most productive. Accord- Vietnamese aquamarines are generally light to
Figure 12. These faceted

garnets from Luc Yen
(left) and Kon Tum
(right) range from 1.5 to
2.2 ct. Photos by Nguyen
Duc Trung Kien.
A B C
Figure 13. Vietnamese garnets may contain mineral inclusions of zircon (A), quartz (B), and monazite (C).
Photomicrographs by Le Thi-Thu Huong; magnified 35.
Figure 14. These irradiated beryl crystals (up to 5 cm identified low amounts of K and Na and high
long) were being sold in the Vietnamese market as amounts of Fe and Cs compared to other sources (Le
untreated heliodor. Photo by Nguyen Duc Trung Kien.
et al., 2011). Although emerald and more recently he-
liodor finds have been reported in nearby Chinese
and Cambodian localities (Laurs, 2010), they have
not yet been uncovered in Vietnam. Aquamarine is
the only gem variety of beryl produced there so far.
According to some Vietnamese dealers, a large vol-
ume of pale aquamarine from Vietnam has been ir-
radiated in Laos and then sold back on the domestic
market as natural heliodor (figure 14).
Green Orthoclase. Recently, gem-quality green

feldspar has been sold in gem markets in Luc Yen and
Hanoi as amazonite, the term for bluish green micro-
cline. The material has been recovered with tourma-
line from pegmatite bodies reportedly located near
Minh Tien. The feldspar is pale to moderate green,
medium blue with moderate saturation. While no in- and is mostly translucent to semitransparent (figure
ternal features are considered locality specific, chem- 15). Although green transparent material has been re-
ical data of samples from Thuong Xuan have ported in the area since the beginning of the 2000s
Figure 15. This green orthoclase crystal (left, ~10 cm wide) was purchased in Luc Yen and contains some
transparent areas that could be faceted. Most green orthoclase from Luc Yen is of cabochon quality (center,
7.8 and 8.5 ct). Faceted samples are very rare in the market (right, 1.5 cm long). Left photo by Le Thi-Thu
Huong; center and right photos by Nguyen Duc Trung Kien.
TABLE 5. Chemical composition of tourmaline RAMAN SPECTRA

(elbaite) from Luc Yen, Vietnam.a
Oxides Pink Green Reddish Yellow Data from
(wt.%) brown Wilson (2007)b
SiO2 36.28 36.97 36.40 36.51 36.3536.65

TiO2 bdl 0.25 0.38 0.20 bdl0.26
INTENSITY
Orthoclase
B2O3 11.01 10.84 10.93 11.03 10.7511.04
Al2O3 40.08 41.63 37.88 42.27 38.0742.70
Cr2O3 bdl 0.26 bdl bdl nr Luc Yen feldspar
V2O3 bdl 0.12 bdl 0.05 bdl0.01

Bi2O3 bdl bdl bdl bdl bdl0.01
Microcline
FeO 0.02 0.03 3.20 0.11 bdl4.88
MnO 0.09 0.01 0.37 bdl 0.026.08 1200 1000 800 600 400 200
CuO 0.01 bdl bdl 0.04 nr RAMAN SHIFT (cm-1)

PbO 0.20 bdl 0.20 0.02 nr
MgO 0.02 0.02 bdl 0.03 bdl0.04 Figure 16. This representative Raman spectra of Luc
CaO 2.25 0.47 0.95 0.48 0.331.93 Yen green feldspar shows a closer resemblance to or-
Li2O 2.18 1.92 2.03 2.12 1.461.98 thoclase than microcline.
Na2O 1.29 2.57 2.17 2.58 0.652.45
K2O 0.01 bdl 0.02 bdl 0.010.04
F 0.90 0.14 0.93 0.05 0.851.22 the band shapes in the specimens Raman spectra al-
O=F 0.38 0.06 0.39 0.02 0.360.55 lowed a further distinction between microcline and
Total 93.98 95.16 95.06 95.47 95.4597.17 orthoclase. Due to the partially disordered arrange-
ment of Al-Si in tetrahedral sites, orthoclase has
Ions on the basis of 31 (O,OH,F)
wider Raman peaks (Freeman et al., 2008). A well-
Si 5.905 6.016 5.924 5.942 nr resolved triplet in the 515450 cm-1 range and a dou-
Ti bdl 0.039 0.059 0.031 nr blet at 290250 cm-1 widen to the less-resolved
B 3.095 3.047 3.071 3.100 nr features in the orthoclase spectrum (figure 16).
Al 7.688 7.986 7.266 8.108 nr Raman spectra of four samples (the crystal, in addi-
Cr bdl 0.033 bdl bdl nr tion to faceted and cabochon samples) showed a
V bdl 0.014 bdl 0.005 nr closer resemblance to orthoclase than to microcline.
Bi bdl bdl bdl bdl nr Our findings are consistent with the infrared spec-
Fe 0.003 0.004 0.435 0.015 nr troscopy results reported by Laurs et al. (2005).
Mn 0.012 0.002 0.051 0.000 nr
Cu 0.002 bdl bdl 0.005 nr Topaz. Topaz is recovered along with aquamarine in
Pb 0.009 bdl 0.009 0.001 nr mining areas such as Thuong Xuan and Thach
Mg 0.004 0.005 bdl 0.007 nr Khoan. Other sources include Bao Loc (Lam Dong
Ca 0.392 0.081 0.166 0.084 nr Province) and Tu Le (Yen Bai). Among these, the peg-
Li 1.429 1.261 1.329 1.388 nr matite-hosted topaz at Thuong Xuan has the most
Na 0.460 0.915 0.773 0.919 nr potential, and this area is estimated to contain ~40
K 0.001 bdl 0.004 bdl nr tonnes of colorless topaz (Nguyen et al., 1995). At the
F 0.463 0.072 0.476 0.024 nr other mining areas, topaz is extracted from placers
a
Values from this study represent the average of four points per sample. that yield high-quality gem material suitable for
All iron is reported as FeO. Abbreviations: bdl = below detection limit, faceting. The crystals, which tend to be broken dur-
nr = not reported.
b
Colors included pink, yellow, green, olive, and gray.
ing alluvial transport, are typically colorless (rarely
blue) with high clarity. Colorless and irradiated blue
topaz from Vietnam are shown in figure 17.
(Ponahlo et al., 2001), the lead author continues to Quartz. Rock crystal and smoky quartz are found in
see rare facet-grade stones in the market (figure 15, pegmatites in several districts: Thuong Xuan, Ky Son
right). (Nghe An Province), and Thach Khoan. Amethyst is
X-ray powder diffraction analysis of a crystal mined at Chu Boc (Gia Lai Province). Rose quartz has
sample identified it as orthoclase. A comparison of been found near Da Nang, and smoky quartz near
TABLE 6. Gemological characteristics of peridot from the Central Highlands of Vietnam.
Property No. samples Observations Data from Kammerling and Koivula (1995)
Color 43 rough and Yellowish green to olive green or brownish Medium light to medium dark yellowish green
faceted green to brownish green of low to moderate saturation
Diaphaneity 43 rough and Semitransparent to transparent Transparent
faceted
Refractive 26 faceted nx = 1.6501.652 nx = 1.650
indices
ny = 1.6651.669 ny = 1.6651.667
nz = 1.6861.690 nz = 1.6871.688
Birefringence 26 faceted 0.0360.038 0.0370.038
Optical 26 faceted Biaxial negative nr a
character
Specific gravity 26 faceted 3.323.37 3.34 0.01
Pleochroism 26 faceted Weak, brownish to yellowish green Weak, very slightly brownish green and
yellowish green
UV fluorescence
Long-wave 26 faceted Inert nr
Short-wave 26 faceted Inert nr
Internal 26 faceted Spinel, sphalerite, lily pad inclusions Chromian spinel(?), biotite mica(?), lily pad
features inclusions surrounding negative crystals, smoke-
like veiling, optically active intergrowth
a
Lam Dong. Large citrine gemstones (figure 18) have Pearl. Vietnam has many natural advantages for salt-
been cut from rough material mined near Cam Ranh water pearl farming: a long coastline with numerous
(Khanh Hoa Province). bays, large islands, and an ideal water temperature.
Zircon. Together with basaltic sapphires, zircon is re- The marine area suitable for pearl culture amounts
covered from placers in the provinces of Kon Tum, to about 568,424 hectares (Nguyen, 2008). Nguyen (a
Dak Lak, Dak Nong, Gia Lai, Lam Dong, and Binh biologist and owner of a pearl farm in Ha Long Bay)
Thuan. The zircon ranges from colorless to orange, has found that the waters surrounding many large is-
brownish orange, and reddish brown. The crystals, lands, including Phu Quoc, Con Dao, Phu Quy, Ly
typically combinations of the bipyramid and the Son, Con Co, Bach Long Vi, and Co To, are suitable
tetragonal prism, are usually etched and waterworn for the culture of Pinctada maxima and P. margari-
and between 0.5 and 2.2 cm in dimension (figure 19). tifera. Several bays in the north, namely Van Don,
The reddish brown zircon is typically heated to turn Bai Tu Long, Ha Long, and Lan Ha, are favorable for
it blue, orange, or colorless. akoya (P. martensii, P. fucata). The production of
Figure 17. The topaz

crystal on the left (~4
cm tall) is representa-
tive of material from
Thanh Hoa Province.
The Vietnamese irradi-
ated blue topaz shown
on the right ranges
from 16.7 to 29.8 ct.
Photos by Le Thi-Thu
Huong.
TABLE 7. Chemical composition of peridot from the

Central Highlands of Vietnam.a
Oxides (wt.%) Gia Lai Dak Lak Lam Dong
SiO2 41.95 41.78 41.74

Al2O3 0.01 bdl bdl
Cr2O3 0.03 0.04 0.04
FeO 8.47 8.49 8.48
MnO 0.11 0.15 0.12
MgO 50.07 49.95 49.99
CaO 0.05 0.04 0.05
NiO 0.37 0.36 0.37
Total 101.06 100.80 100.80
Cations per 4 oxygens

Si 1.007 1.008 1.008
Al 0.000 bdl bdl
Cr 0.001 0.001 0.001
Fe 0.171 0.170 0.171
Figure 18. Citrine from Khanh Hoa Province is known
Mn 0.002 0.002 0.003
for its large size. The square cushion cut measures 4.2
Mg 1.798 1.795 1.797 4.2 cm. Photo by Le Thi-Thu Huong.
Ca 0.001 0.001 0.001
Ni 0.007 0.007 0.007
a
Japanese experts. Today, the farms are operated by
Values represent the average of five points per sample, and one
sample from each locality was analyzed. Abbreviation: bdl = below Vietnamese technicians. The akoyas typically range
detection limit. Ti and V were analyzed but not detected. from 5 to 8 mm in diameter, with natural golden or
gray colors (figure 20). Their nacre layer can reach 1
1.5 mm in 12 months. Black cultured pearls are
freshwater cultured pearls from Hyriopsis cumingii, mainly farmed around southern islands such as Phu
Cristaria bialata, and Sinanodonta elliptica has oc- Quoc. They vary from 4 to 8 mm. Freshwater cultured
curred on a smaller scale in lakes throughout the pearls are typically pink, cream, brown, and gray,
country, especially Thac Ba, Cam Son, Hoa Binh, Ke and range from 6 to 12 mm. Vietnams pearl farms are
Go, and Tri An. still small scale and mostly private. The annual pro-
During the past 20 years, Vietnamese pearl farms duction of one akoya farm in Ha Long Bay, for exam-
have developed under the training and supervision of ple, averages between 12 and 15 kg.
TABLE 8. Gemological characteristics of garnet from Luc Yen and Kon Tum, Vietnam.
Luc Yen Kon Tum

Property No. samples Observations No. samples Observations
(this study) (this study)
Color 19 rough and Brownish red 12 rough and Brownish red

faceted faceted
Diaphaneity 19 rough and Semitransparent to transparent 12 rough and Semitransparent to transparent
faceted faceted
Refractive indices 10 faceted 1.8001.805 6 faceted 1.7901.795
Specific gravity 10 faceted 4.084.15 6 faceted 3.923.96
UV fluorescence
Long-wave 10 faceted Inert 6 faceted Inert
Short-wave 10 faceted Inert 6 faceted Inert
Internal features 10 faceted Monazite, quartz, apatite, and zircon 6 faceted Monazite, quartz, apatite, and zircon
Hollow tubes filled with fluid Hollow tubes filled with fluid
TABLE 9. Chemical composition of garnet from

Luc Yen and Kon Tum, Vietnam.
Oxides Luc Yen Luc Yen Luc Yen Kon Tum Kon Tum Kon Tum
(wt.%) 1 2 3 1 2 3
SiO2 36.52 36.23 36.43 39.97 40.63 40.75

TiO2 0.01 bdl 0.03 0.01 0.01 bdl
Al2O3 21.78 21.84 21.90 24.09 23.98 23.88
Cr2O3 bdl 0.04 0.03 0.06 0.01 0.10
V2O3 bdl 0.01 bdl bdl 0.02 bdl
FeO 36.91 37.12 37.08 16.47 16.50 16.15
MnO 0.39 0.38 0.47 0.57 0.58 0.56
MgO 3.32 3.27 3.30 17.33 17.15 17.16
CaO 1.06 1.04 1.15 1.30 1.30 1.27
Na2O 0.07 0.04 0.04 0.00 0.00 0.04
Total 100.06 99.96 100.44 99.79 100.18 99.91
Cations per 12 oxygens
Si 2.941 2.929 2.934 2.924 2.950 2.970
Ti 0.001 bdl 0.000 0.000 0.001 bdl
Al 2.067 2.081 2.081 2.077 2.053 2.051
Cr bdl 0.002 0.002 0.003 0.001 0.005
V bdl 0.000 bdl bdl 0.000 bdl
Fe 2.486 2.511 2.498 1.008 1.002 0.985 Figure 20. Akoya cultured pearls from Ha Long Bay
Mn 0.027 0.026 0.032 0.035 0.036 0.035 typically display golden and gray colors. Photo by
Mg 0.399 0.394 0.396 1.891 1.857 1.865 Pham Van Long.
Ca 0.091 0.090 0.099 0.102 0.101 0.099
Na 0.012 0.006 0.006 0.000 0.000 0.006
China Sea. Melo pearls are recovered off the coast of
a
Values represent the average of five points per sample, and three samples Vietnam, Thailand, Myanmar, and Malaysia (Par-
from each locality were analyzed. Abbreviation: bdl = below detection limit.
dieu, 2009). Vietnam is the leading source of these
pearls (e.g., figure 21). They are found in Ha Long Bay
and along the southern coast from Nha Trang to
Melo pearls are natural non-nacreous concretions Phan Thiet. Melo pearls have apparently not been
produced by the marine gastropod Melo melo. This successfully produced by culturing, and they remain
large snail lives mainly in the waters of the South extremely rare and expensive.
Figure 21. This fine 161 ct Melo pearl is from Phan

Figure 19. These pieces of zircon from Lam Dong Thiet, on the south coast of Vietnam. Photo by Pham
range from 0.5 to 2.2 cm. Photo by Pham Van Long. Van Long.
CONCLUSIONS for blue, green, and yellow sapphire as well as peridot

Due to its geologic position along the margins of two and zircon in the Central Highlands. Of greatest com-
cratons, Vietnam is endowed with a diversity of gem mercial potential are the marble-hosted ruby, sap-
minerals. These include ruby, sapphire, spinel, tour- phire, and spinel deposits in Yen Bai and Nghe An.
maline, garnet, peridot, aquamarine, topaz, zircon, Compared to its gem wealth, Vietnams mining
green orthoclase, and several quartz varieties. The two and pearl farming sectors are still relatively small and
important geologic events affecting gem formation in undeveloped, leaving many potential resources unex-
Vietnam were (1) the Himalayan orogeny (5021 Ma), ploited. This situation is likely to change in the near
which resulted in ruby, sapphire, and spinel in the future with greater emphasis by the government on
northern provinces of Yen Bai and Nghe An; and (2) developing the countrys gem industry and promoting
basaltic volcanism (~6.5 and ~1 Ma), which accounts its resources on an international level.
ABOUT THE AUTHORS ACKNOWLEDGMENTS

Dr. Huong (letth@vnu.edu.vn) is a lecturer in mineralogy and Thanks are given to Nguyen Huy Truong, a gem dealer in Luc Yen,
gemology, Dr. Khoi is an associate professor, and Dr. Nhung is a for loaning tourmaline samples, and to Pham Tuong Minh, a gem
retired associate professor in the Faculty of Geology at the Viet- dealer in Hanoi, for loaning the faceted green orthoclase for our
nam National University, Hanoi. Dr. Hger is senior scientist at the research. The first author would like to give special thanks to Dr.
Centre for Gemstone Research at Johannes Gutenberg Univer- Henry Hnni (GemExpert, Basel, Switzerland) and to a friend,
sity in Mainz, Germany, lecturer in the Gemstone and Jewellery Hans Joachim Szanto (Mainz, Germany), for supplying the cabo-
Design Department at the University for Applied Sciences in Idar- chon ruby and sapphire and faceted garnet samples for this study.
Oberstein, and managing director of the Center for Gemstone We are grateful to Drs. Joachim Kusz and Maciej Zubko (Univer-
Research in Idar-Oberstein. Dr. Hofmeister is professor and dean sity of Silesia, Katowice, Poland) for their helpful discussions on
of the Faculty of Chemistry, Pharmacy and Geosciences at Jo- the XRD analysis of the green orthoclase samples. We thank Dr.
hannes Gutenberg University, and head of the Centre for Gem- Gaston Giuliani (French National Center for Scientific Research at
stone Research. Dr. Wehmeister is a scientist at the Centre for the Center for Petrographic and Geochemical Research in Nancy)
Gemstone Research. Dr. Hauzenberger is an associate professor and many other reviewers for critiquing an earlier version of the
at the Institute of Geosciences at Karl Franzens University in manuscript. This research is part of a project supported by the
Graz, Austria. Dr. Schwarz is senior scientist and head of re- Vietnam National Foundation for Science and Technology Devel-
search at the Gbelin Gem Lab in Lucerne, Switzerland. Dr. Long opment (NAFOSTED, project 105.02-2010.20). This manuscript
is a gemologist at the Centre for Gem and Gold Research and was financially aided by Teaching and Research Improvement
Identification in Hanoi. Grants from the Vietnam National University, Hanoi.
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Gemstones From Vietnam An Update

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Huong G&G Fall 2012_Layout 1 9/28/12 4:29 PM Page 158

GEMSTONES FROM VIETNAM:

Gem Mining Areas

2 Phu Tho: Quartz, topaz, aquamarine, garnet

2 Hanoi 5 Quang Nam: Ruby, sapphire

Ha Long 6 Da Nang: Rose quartz

Thanh Hoa 9 Dak Lak: Zircon, peridot, sapphire

14 Dong Nai: Sapphire

Indochina craton Basalts

Kon Tum massif

Figure 3. Ruby and sap-

Figure 5. In Luc Yen,

figure 5, left), sometimes associated with clinochlore

TABLE 2. Gemological characteristics of gem corundum from other localities in Vietnam.

TABLE 3. Gemological characteristics of spinel from Luc Yen, Vietnam.

Property No. samples Observations Data from the literature

Diaphaneity 114 rough and Semitransparent to transparent nr a

Figure 7. Luc Yen spinel

Figure 8. The principal

Figure 9. Tourmaline from Luc

Chemical analyses of our samples showed that

Figure 11. Vietnamese

TABLE 4. Gemological characteristics of tourmaline from Luc Yen, Vietnam.

Property No. samples Observations Data from the literature

Figure 12. These faceted

Green Orthoclase. Recently, gem-quality green

TABLE 5. Chemical composition of tourmaline RAMAN SPECTRA

SiO2 36.28 36.97 36.40 36.51 36.3536.65

V2O3 bdl 0.12 bdl 0.05 bdl0.01

CuO 0.01 bdl bdl 0.04 nr RAMAN SHIFT (cm-1)

TABLE 6. Gemological characteristics of peridot from the Central Highlands of Vietnam.

Figure 17. The topaz

TABLE 7. Chemical composition of peridot from the

SiO2 41.95 41.78 41.74

Cations per 4 oxygens

Luc Yen Kon Tum

Color 19 rough and Brownish red 12 rough and Brownish red

TABLE 9. Chemical composition of garnet from

SiO2 36.52 36.23 36.43 39.97 40.63 40.75

Figure 21. This fine 161 ct Melo pearl is from Phan

CONCLUSIONS for blue, green, and yellow sapphire as well as peridot

ABOUT THE AUTHORS ACKNOWLEDGMENTS

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