IGNEUS ROCK ACID AND INTERMEDIETIC ROCKS

Winda Asriana

Praktikan Mineralogi dan Petrologi

ABSTRACT

There are many types of rocks resulting from natural processes, and each type of rock is divided
again to produce different rocks. One example is the type of igneous rock, igneous rock, which is rock
formed by freezing magma / lava or crystallization of minerals in the form of aggregation and inlocking.
From the formation process of igneous rocks, it produces rocks of different types, namely granite,
andesite, dacite, and syenite. Seeing the many types of rocks that are divided, the purpose of this
practicum is to identify the types of igneous rocks. The types of rock used are granite, andesite, syenite,
and syenite. The rock is analyzed by the practitioner starting from rock color, rock structure, rock texture
(crystallinity, granularity, fabric), and the minerals that form the rock. From the results of the practicum,
the practitioner can recognize the characteristics of several types of igneous rock. From the practicum, it
can be concluded that rocks are classified based on their mineral and chemical composition, with the
texture of the elemental particles and the process of their formation.

I. INTRODUCTION and also does not have a fixed chemical

composition and physical properties and
Stone is part of the natural wealth of is formed in nature. There are many
Indonesia. Rock is the constituent of the types of rocks resulting from natural
earth's crust and is also an aggregate of processes, and each type of rock is
hardened minerals that occur as a result divided again to produce different rocks.
of natural processes such as, freezing,
weathering, settling, and also chemical In this practicum, the focus is on
processes. Rocks on earth can be igneous rocks, where this type of rock is
divided into 3 groups and are usually further divided based on the place of
divided according to the process of freezing and also based on its content.
formation. First is igneous rock, which Igneous rock is rock resulting from the
is formed from incandescent magma that freezing of magma, which is the molten
cools to become solid. The second is and incandescent mass in the earth.
sedimentary rock, this rock is formed These rocks are the materials that make
due to the process of compaction of up the earth's crust and consist of a
sediment, the result of erosion or rock collection of rock-forming minerals
that occurs due to the accumulation of which in nature these rocks have
pre-existing rock. And the third is the properties that are influenced by the
type of metamorphic rock which is minerals that form these rocks.
formed from the metamorphism of a
pre-existing rock type. The properties of these minerals are
determined by their chemical
Rock is an aggregation or collection composition, crystal shape, cleavage
of minerals (similar or not similar), in a area, density and hardness. The purpose
certain ratio, usually not homogeneous of this practicum is to identify types of
 igneous rocks. And the purpose of is closely related to its chemical and
carrying out this practicum is so that the mineralogical composition, then the texture is
practitioner can recognize and classify related to the history of its formation and its
the types of igneous rock. occurrence. The structures of igneous rocks are
massive / compact structures, structures due to
II. LITERATURE REVIEW the release of volatile materials (vesiculation,
Igneous rock is the result of freezing of a amygdaloidal), the surface structure of the
material from high temperature molten material solution phase (Ir.K.M. Arsyad, M.Sc, 2017).
that originates from a deep part of the earth
called magma. At the time the Earth's crust was III. METHODOLOGY
formed, it was thought that the entire rock was
igneous rock. Igneous rocks or often called This practicum will be held on
igneous rocks are rocks that are formed from Saturday, March 6, 2021 at 9.00 AM
one or several minerals and are formed as a WITA. Located at Makassar State
result of freezing from magma. Based on the University, Faculty of Mathematics and
texture, this igneous rock can be divided into Natural Sciences, majoring in
plutonic and volcanic igneous rock. The geography. The methodology used is the
difference between the two can be seen from the megascopic / invisible method of
size of the minerals that make up the rock. analysis, in identifying rock types we
Plutonic igneous rocks are generally formed used 5 rock samples. In identifying rock
from the relatively slower freezing of magma so characteristics, we classify them into 4
that the minerals constituting relatively large. categories, namely color, texture,
Examples of plutonic igneous rocks include structure, and minerals contained in
gabbro, diorite, and granite (which are often rocks. The characteristics of the rocks
used as home decorations). Meanwhile, volcanic that have been identified will then be
igneous rocks are generally formed from named according to the Fenton naming
freezing magma very quickly (for example due table.
to volcanic eruptions) so that the constituent
minerals are smaller. Examples are basalt, IV. RESULTS AND DISCUSSION
andesite (which is often used as a house In identifying this igneous rock, one of the
foundation), and dacite (Ir.K.M. Arsyad, M.Sc, properties of the rock that needs to be looked at
2017). is color, because the color of the rock usually
Based on the place of freezing, igneous represents the minerals that form the igneous
rocks are divided into extrusive and intrusive rock itself. Apart from the color of the rock
igneous rocks. This in turn will cause properties that need to be seen is the texture,
differences in the texture of each of these rocks. where the texture is the appearance of the rock
The appearance of exposed igneous rock is the related to the size, shape, and arrangement of the
first thing we should pay attention to. This mineral grains in the rock. Then what needs to
appearance is known as an igneous rock be seen again is the structure, where the
structure (Sebastian, 2016). structure is the appearance of the relationship
The definition of rock texture refers to the between different rock parts. And the last one is
appearance of mineral grains in it, which the mineral composition of rock-forming
includes the level of crystallization, grain size, minerals, namely minerals found in igneous
grain shape, granularity, and the relationship rocks, including: quartz, mica, feldspar, olivine,
between the grains (fabric). If the color of a rock
pyroxene. Minerals found in metamorphic rocks dioxide (SiO2) range of 57-63% as
include: quartz, mica, feldspar, carbont, clay depicted in the TAS diagram. The
minerals. mineral makeup is usually dominated by
plagioclase plus pyroxene and / or
Andesit hornblende.

Andesite stone is widely used in

megalithic buildings, temples and
pyramids. Likewise, many tools from
prehistoric times use this material, for
example: sarcophagi, punden terraces,
stone mortars, stone tables, statues, etc.

Granit

In the first observation, we

identified the rock with the serial
number of display number 60. This rock
has a grayish white color, and has a
slightly white color on its surface. The
texture of this rock is afanitic, this is due
to the presence of mafic (bases), this
characteristic is very visible in the
presence of a rather gloomy (dark) color
In the second sample, the fresh
of the rock. In addition, this rock does
color is: Grayish white, while the
not have cracks or gas holes on its
weathered color is brownish yellow. The
surface so that the overall structure of
texture is hypocrystalline, composed of
this rock is massive. Based on the color
partly crystals and glass. Granularity:
of this rock, its mineral composition is
faneritic where there is Faneroclas,
plagioclase and biotite. Based on the
namely pyroxene minerals. The fabric is
physical properties the rock name can be
divided into shapes and relations, for the
determined is andesite, the mineral
shape of this rock, namely: euhedral-
grains that make up the rock that cannot
subhedral, while for the relation,
be seen with the naked eye.
namely: equigranular because there are
The process of forming andesite pyroxene minerals which has the same
rocks affects its physical characteristics. size as the base mass. The structure is
Andesite rock is an external (extrusive) massive. The mineral composition of
igneous rock. The cooling process of this rock consists of a gray base mass,
andesite rocks is very fast, resulting in a bone white quartz, and black pyroxine.
rock with a smooth texture. From the above explanation, it can be
concluded that with the suitability of the
Andesite is an intermediate type fenton diagram, it can be called the rock,
between basalt and dacite, with a silicon Granite.
 Beneath the earth's surface, that are clearly visible. The granularity
magma, a mixture of molten and semi- is faneritic, the constituent mineral
molten rock, slowly crystallizes. These crystals are clearly visible and can be
crystals are composed of feldspar, mica, distinguished by the ordinary eye or
quartz and other minerals that together with the help of a loop. Febrik is the
create unique patterns and colors. Then, relationship between crystals or
these crystals cool very slowly in a arrangement between crystals with one
deeply buried location to produce another. The shape of the crystals is
mineral grains. This natural process took euhedral and subhedral, where the
millions of years to form, giving granite planes of the cystals are equal and
its strength with a unique mark that regular. the relation is: inequigranular
makes it special. where the grain size of the crystals that
make up the rock is the same. While the
Granite is an igneous rock in a stone structure is massive
holocrystalline, faneritic, coarse grained
texture, containing minerals: quartz 10- The petrogenesis explains that
4%, feldspar potassium 30-60%, sodium Dacite in the formation process is an
plagioclase 0-35%, mafis minerals igneous rock that is included in the
(biotite, hornblend) 35-10%. volcanic type, because dacite in the
process of formation undergoes rapid
The benefits of granite, namely magma cooling. The process of dacite
granite, are known to have better quality formation at temperatures around 900
than other rocks such as sand and sekitarC - 1200 C.
marble. The acidic nature of granite
rocks makes this rock resistant to acid The silica content contained in
rain so it is widely used in building dacite ranges from 52% - 66%. In the
construction warehouses. process of its formation dacite is a felsic
extrusion rock which is intermediate in
Dasit composition between andesite and
rhyolite. In its formation it is often
found joining with andesite, and forming
lava flows, as well as embankments.

Dasit is widely used as a stone

ornament for walls and floors of
buildings or for split stone for building
foundations. Dasit aggregates can be
used as fill material in various
construction projects.

Diorit
In the 3rd observation, the fresh
colors are: grayish white while the
weathered color is brownish gray. The
texture of the crystallinity is
Holocrystalline, composed of crystals
 include: As a wall ornament stone. as
gemstones or stones used as jewelery.

Syenit

In the fourth sample, the color is

fresh from white to gray, the weather is
yellowish brown. Crystallility:
hypocrystalline, ganulitas:
porphyroafanitic, Shape: Anhedral,
Equigranular relation. Diorite rocks In the fifth sample, where the
contain large amounts of calcixodic fresh color is grayish white and the
plagioclase feldspar with many sodic weathered color is brownish black. The
types. textures where the crystallinity are
Holocrystalline there is an arrangement
There is a mixing process of of clearly visible crystals. The
basaltic magma and also granite magma granularity is the faneritic of the
which will rise on the continental plate constituent mineral crystals. rock lop.
both dike and sill. The melt will produce The fabric is subhedral, while the
a composition between basalt and relation is inequigranular. The structure
granite. This melt will slowly crystallize is massive. The mineral composition of
and then form a rock known as diorite this rock consists of a gray base mass,
rock gray feldspar. From the above
explanation, it can be concluded that
Rocks with more alkaline with the suitability of the fenton
plagioclase are called gabbro. If there diagram, it can be called the rock,
are many penokris it is called diorite Syenid.
porphyry. Diorite consists of
approximately 65% plagioclase and 35% The rocks on this earth must
dark silicate minerals such as biotite and have undergone a series of processes
augite. Accessory minerals are quartz, before becoming a rock, as is the case
pharmacy, calcite, chlorite, granite, and with this sienite stone. This sienite stone
epidote. is formed by minerals such as K.
Felsda's orthoclasts, plagioclase, biotite,
Diorite stone is more widely epidote, sphene, opaque minerals, clays
used in the building sector. Some of the and still visible polyomtetic twin
benefits possessed by diorite stone reliability.
 Syenite composition is Tim Asisten Mineralogi dan Petrologi, 2021.
dominated by bases such as plagioclase, Buku Panduan Praktikum Mineralogi dan
amphibole. The feldspar component of petrologi. Universitas negeri Makassar.
syenite is predominantly alkaline Makassar.
(usually orthoclast). Plagioclase feldspar
may be present in a small proportion, Lelyani Kin Khosama. 2012. Kuat
less than 10%. feldspar like this is often TekanBeton BeragregatKasar batuan
inserted as a component of rock pertit. Tuff Putih dan Batuan Andesit. Jurnal
Ilmiah Media Engineering. Fakultas
The benefits of syenite stones Teknik Universitas Sam Ratulangi.
for human life are inseparable from the Manado.
name stone, almost all human activities
take advantage of the existence of rocks W. T. Huang,1962, Modul ekskursi Endapan
to be used in various things such as Mineral, Program  Studi Teknik Geologi.
building a building, as a mixture of Institut Teknologi Bandung.
building materials, to decorate a house,
to make jewelry. The characteristics of
different stones make the uses or
functions that these stones have are also
different.

V. CLOSING

Based on the results of the

practicum, it can be concluded that the
characteristic feature of igneous rocks is
their crystalline appearance, which has
small crystal units that bind to one
another. Important things that must be
observed in igneous rocks are the origin
of the event, the rock type, texture,
color, rock type, and mineral
composition.

BIBLIOGRAPHY

Ir.K.M. Arsyad, M.Sc. 2017. Modul geologi

Teknik Pelatihan Perencanaan
Bendungan Tingkat Dasar. Bandung.

Sebastian. 2016. Geologi dan Petrogenesa

Batuan Andesit Desa Tangkil dan sekitar
KecamatanTirtoyudoKabupaten Malang
Provinsi Jawa Timur. Sains dan
Teknologi Terapan. Malang