Sany Hydraulic Excavator SY18 Operation Manual - Bedienungshandbuch DE 2017

Sany Hydraulic Excavator SY18

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feet in diameter. The decomposing surface very commonly assumes
a coating of a rusty iron colour, from the oxidation of ferruginous
matter, so abundant in the traps in which augite or hornblende
occur; or, in the felspathic varieties of trap, it acquires a white
opaque coating, from the bleaching of the mineral called felspar. On
examining any of these volcanic rocks, where they have not suffered
disintegration, we rarely fail to detect a crystalline arrangement in
one or more of the component minerals. Sometimes the texture of
the mass is cellular or porous, or we perceive that it has once been
full of pores and cells, which have afterwards become filled with
carbonate of lime, or other infiltrated mineral.

Most of the volcanic rocks produce a fertile soil by their

disintegration. It seems that their component ingredients, silica,
alumina, lime, potash, iron, and the rest, are in proportions well
fitted for vegetation. As they do not effervesce with acids, a
deficiency of calcareous matter might at first be suspected; but
although the carbonate of lime is rare, except in the nodules of
amygdaloids, yet it will be seen that lime sometimes enters largely
into the composition of augite and hornblende. (See Table, p. 377.)

Cones and Craters.—In regions where the eruption of volcanic

matter has taken place in the open air, and where the surface has
never since been subjected to great aqueous denudation, cones and
craters constitute the most striking peculiarity of this class of
formations. Many hundreds of these cones are seen in central
France, in the ancient provinces of Auvergne, Velay, and Vivarais,
where they observe, for the most part, a linear arrangement, and
form chains of hills. Although none of the eruptions have happened
within the historical era, the streams of lava may still be traced
distinctly descending from many of the craters, and following the
lowest levels of the existing valleys. The origin of the cone and
crater-shaped hill is well understood, the growth of many having
been watched during volcanic eruptions. A chasm or fissure first
opens in the earth, from which great volumes of steam and other
gases are evolved. The explosions are so violent as to hurl up into
the air fragments of broken stone, parts of which are shivered into
minute atoms. At the same time melted stone or lava usually
ascends through the chimney or vent by which the gases make their
escape. Although extremely heavy, this lava is forced up by the
expansive power of entangled gaseous fluids, chiefly steam or
aqueous vapour, exactly in the same manner as water is made to
boil over the edge of a vessel when steam has been generated at
the bottom by heat. Large quantities of the lava are also shot up into
the air, where it separates into fragments, and acquires a spongy
texture by the sudden enlargement of the included gases, and thus
forms scoriæ, other portions being reduced to an impalpable powder
or dust. The showering down of the various ejected materials round
the orifice of eruption gives rise to a conical mound, in which the
successive envelopes of sand and scoriæ form layers, dipping on all
sides from a central axis. In the mean time a hollow, called a crater,
has been kept open in the middle of the mound by the continued
passage upwards of steam and other gaseous fluids. The lava
sometimes flows over the edge of the crater, and thus thickens and
strengthens the sides of the cone; but sometimes it breaks it down
on one side, and often it flows out from a fissure at the base of the
hill (see fig. 436.).[368-A]
Fig. 436.

Part of the chain of extinct volcanos called the Monts

Dome, Auvergne. (Scrope.)

Composition and nomenclature.—Before speaking of the

connection between the products of modern volcanos and the rocks
usually styled trappean, and before describing the external forms of
both, and the manner and position in which they occur in the earth's
crust, it will be desirable to treat of their mineral composition and
names. The varieties most frequently spoken of are basalt,
greenstone, syenitic greenstone, clinkstone, claystone, and trachyte;
while those founded chiefly on peculiarities of texture, are porphyry,
amygdaloid, lava, tuff, scoriæ, and pumice. It may be stated
generally, that all these are mainly composed of two minerals, or
families of simple minerals, felspar and hornblende; some almost
entirely of hornblende, others of felspar.

These two minerals may be regarded as two groups, rather than

species. Felspar, for example, may be, first, common felspar, that is
to say, potash-felspar, in which the alkali is potash (see table, p.
377.); or, secondly, albite, that is to say, soda-felspar, where the
alkali is soda instead of potash; or, thirdly, Labrador-felspar
(Labradorite), which differs not only in its iridescent hues, but also in
its angle of fracture or cleavage, and its composition. We also read
much of two other kinds, called glassy felspar and compact felspar,
which, however, cannot rank as varieties of equal importance, for
both the albitic and common felspar appear sometimes in
transparent or glassy crystals; and as to compact felspar, it is a
compound of a less definite nature, sometimes containing both soda
and potash; and which might be called a felspathic paste, being the
residuary matter after portions of the original matrix have
crystallized.

The other group, or hornblende, consists principally of two

varieties; first, hornblende, and, secondly, augite, which were once
regarded as very distinct, although now some eminent mineralogists
are in doubt whether they are not one and the same mineral,
differing only as one crystalline form of native sulphur differs from
another.

The history of the changes of opinion on this point is curious and

instructive. Werner first distinguished augite from hornblende; and
his proposal to separate them obtained afterwards the sanction of
Haüy, Mohs, and other celebrated mineralogists. It was agreed that
the form of the crystals of the two species were different, and their
structure, as shown by cleavage, that is to say, by breaking or
cleaving the mineral with a chisel, or a blow of the hammer, in the
direction in which it yields most readily. It was also found by analysis
that augite usually contained more lime, less alumina, and no fluoric
acid; which last, though not always found in hornblende, often
enters into its composition in minute quantity. In addition to these
characters, it was remarked as a geological fact, that augite and
hornblende are very rarely associated together in the same rock;
and that when this happened, as in some lavas of modern date, the
hornblende occurs in the mass of the rock, where crystallization may
have taken place more slowly, while the augite merely lines cavities
where the crystals may have been produced rapidly. It was also
remarked, that in the crystalline slags of furnaces, augitic forms
were frequent, the hornblendic entirely absent; hence it was
conjectured that hornblende might be the result of slow, and augite
of rapid cooling. This view was confirmed by the fact, that
Mitscherlich and Berthier were able to make augite artificially, but
could never succeed in forming hornblende. Lastly, Gustavus Rose
fused a mass of hornblende in a porcelain furnace, and found that it
did not, on cooling, assume its previous shape, but invariably took
that of augite. The same mineralogist observed certain crystals in
rocks from Siberia which presented a hornblende cleavage, while
they had the external form of augite.

If, from these data, it is inferred that the same substance may
assume the crystalline forms of hornblende or augite indifferently,
according to the more or less rapid cooling of the melted mass, it is
nevertheless certain that the variety commonly called augite, and
recognized by a peculiar crystalline form, has usually more lime in it,
and less alumina, than that called hornblende, although the
quantities of these elements do not seem to be always the same.
Unquestionably the facts and experiments above mentioned show
the very near affinity of hornblende and augite; but even the
convertibility of one into the other by melting and recrystallizing,
does not perhaps demonstrate their absolute identity. For there is
often some portion of the materials in a crystal which are not in
perfect chemical combination with the rest. Carbonate of lime, for
example, sometimes carries with it a considerable quantity of silex
into its own form of crystal, the silex being mechanically mixed as
sand, and yet not preventing the carbonate of lime from assuming
the form proper to it. This is an extreme case, but in many others
some one or more of the ingredients in a crystal may be excluded
from perfect chemical union; and, after fusion, when the mass
recrystallizes, the same elements may combine perfectly or in new
proportions, and thus a new mineral may be produced. Or some one
of the gaseous elements of the atmosphere, the oxygen for
example, may, when the melted matter reconsolidates, combine with
some one of the component elements.

The different quantity of the impurities or refuse above alluded to,

which may occur in all but the most transparent and perfect crystals,
may partly explain the discordant results at which experienced
chemists have arrived in their analysis of the same mineral. For the
reader will find that a mineral determined to be the same by its
physical characters, crystalline form, and optical properties, has
often been declared by skilful analyzers to be composed of distinct
elements. (See the table at p. 377.) This disagreement seemed at
first subversive of the atomic theory, or the doctrine that there is a
fixed and constant relation between the crystalline form and
structure of a mineral, and its chemical composition. The apparent
anomaly, however, which threatened to throw the whole science of
mineralogy into confusion, was in a great degree reconciled to fixed
principles by the discoveries of Professor Mitscherlich at Berlin, who
ascertained that the composition of the minerals which had
appeared so variable, was governed by a general law, to which he
gave the name of isomorphism (from ισος, isos, equal, and μορφη,
morphe, form). According to this law, the ingredients of a given
species of mineral are not absolutely fixed as to their kind and
quality; but one ingredient may be replaced by an equivalent portion
of some analogous ingredient. Thus, in augite, the lime may be in
part replaced by portions of protoxide of iron, or of manganese,
while the form of the crystal, and the angle of its cleavage planes,
remain the same. These vicarious substitutions, however, of
particular elements cannot exceed certain defined limits.

Having been led into this digression on the recent progress of

mineralogy, I may here observe that the geological student must
endeavour as soon as possible to familiarize himself with the
characters of five at least of the most abundant simple minerals of
which rocks are composed. These are, felspar, quartz, mica,
hornblende, and carbonate of lime. This knowledge cannot be
acquired from books, but requires personal inspection, and the aid of
a teacher. It is well to accustom the eye to know the appearance of
rocks under the lens. To learn to distinguish felspar from quartz is
the most important step to be first aimed at. In general we may
know the felspar because it can be scratched with the point of a
knife, whereas the quartz, from its extreme hardness, receives no
impression. But when these two minerals occur in a granular and
uncrystallized state, the young geologist must not be discouraged if,
after considerable practice, he often fails to distinguish them by the
eye alone. If the felspar is in crystals, it is easily recognized by its
cleavage: but when in grains the blow-pipe must be used, for the
edges of the grains can be rounded in the flame, whereas those of
quartz are infusible. If the geologist is desirous of distinguishing the
three varieties of felspar above enumerated, or hornblende from
augite, it will often be necessary to use the reflecting goniometer as
a test of the angle of cleavage, and shape of the crystal. The use of
this instrument will not be found difficult.

The external characters and composition of the felspars are

extremely different from those of augite or hornblende; so that the
volcanic rocks in which either of these minerals decidedly
predominates, are easily recognized. But there are mixtures of the
two elements in every possible proportion, the mass being
sometimes exclusively composed of felspar, at other times solely of
augite, or, again, of both in equal quantities. Occasionally, the two
extremes, and all the intermediate gradations, may be detected in
one continuous mass. Nevertheless there are certain varieties or
compounds which prevail so largely in nature, and preserve so much
uniformity of aspect and composition, that it is useful in geology to
regard them as distinct rocks, and to assign names to them, such as
basalt, greenstone, trachyte, and others, already mentioned.

Basalt.—As an example of rocks in which augite greatly prevails,

basalt may first be mentioned. Although we are more familiar with
this term than with that of any other kind of trap, it is difficult to
define it, the name having been used so vaguely. It has been very
generally applied to any trap rock of a black, bluish, or leaden-grey
colour, having a uniform and compact texture. Most strictly, it
consists of an intimate mixture of augite, felspar, and iron, to which
a mineral of an olive green colour, called olivine, is often
superadded, in distinct grains or nodular masses. The iron is usually
magnetic, and is often accompanied by another metal, titanium.
Augite is the predominant mineral, the felspar being in much smaller
proportions. There is no doubt that many of the fine-grained and
dark-coloured trap rocks, called basalt, contained hornblende in the
place of augite; but this will be deemed of small importance after
the remarks above made. Other minerals are occasionally found in
basalt; and this rock may pass insensibly into almost every variety of
trap, especially into greenstone, clinkstone, and wacké, which will be
presently described.

Greenstone, or Dolerite, is usually defined as a granular rock, the

constituent parts of which are hornblende and imperfectly
crystallized felspar; the felspar being more abundant than in basalt;
and the grains or crystals of the two minerals more distinct from
each other. This name may also be extended to those rocks in which
augite is substituted for hornblende (the dolorite of some authors),
or to those in which albite replaces common felspar, forming the
rock sometimes called Andesite.

Syenitic greenstone.—The highly crystalline compounds of the

same two minerals, felspar and hornblende, having a granitiform
texture, and with occasionally some quartz accompanying, may be
called Syenitic greenstone, a rock which frequently passes into
ordinary trap, and as frequently into granite.

Trachyte.—A porphyritic rock of a whitish or greyish colour,

composed principally of glassy felspar, with crystals of the same,
generally with some hornblende and some titaniferous iron. In
composition it is extremely different from basalt, this being a
felspathic, as the other is an augitic, rock. It has a peculiar rough
feel, whence the name τραχυς, trachus, rough. Some varieties of
trachyte contain crystals of quartz.
Fig. 437.

Porphyry.
White crystals of felspar in a dark
base of hornblende and felspar.

Porphyry is merely a certain form of rock, very characteristic of the

volcanic formations. When distinct crystals of one or more minerals
are scattered through an earthy or compact base, the rock is termed
a porphyry (see fig. 437.). Thus trachyte is porphyritic; for in it, as in
many modern lavas, there are crystals of felspar; but in some
porphyries the crystals are of augite, olivine, or other minerals. If the
base be greenstone, basalt, or pitchstone, the rock may be
denominated greenstone-porphyry, pitchstone-porphyry, and so
forth.

Amygdaloid.—This is also another form of igneous rock, admitting

of every variety of composition. It comprehends any rock in which
round or almond-shaped nodules of some mineral, such as agate,
calcedony, calcareous spar, or zeolite, are scattered through a base
of wacké, basalt, greenstone, or other kind of trap. It derives its
name from the Greek word amygdala, an almond. The origin of this
structure cannot be doubted, for we may trace the process of its
formation in modern lavas. Small pores or cells are caused by
bubbles of steam and gas confined in the melted matter. After or
during consolidation, these empty spaces are gradually filled up by
matter separating from the mass, or infiltered by water permeating
the rock. As these bubbles have been sometimes lengthened by the
flow of the lava before it finally cooled, the contents of such cavities
have the form of almonds. In some of the amygdaloidal traps of
Scotland, where the nodules have decomposed, the empty cells are
seen to have a glazed or vitreous coating, and in this respect exactly
resemble scoriaceous lavas, or the slags of furnaces.
Fig. 438.

Scoriaceous lava in part converted

into an amygdaloid.
 Montagne de la Veille, Department
of Puy de Dome, France.

The annexed figure represents a fragment of stone taken from the

upper part of a sheet of basaltic lava in Auvergne. One half is
scoriaceous, the pores being perfectly empty; the other part is
amygdaloidal, the pores or cells being mostly filled up with
carbonate of lime, forming white kernels.

Scoriæ and Pumice may next be mentioned as porous rocks,

produced by the action of gases on materials melted by volcanic
heat. Scoriæ are usually of a reddish-brown and black colour, and
are the cinders and slags of basaltic or augitic lavas. Pumice is a
light, spongy, fibrous substance, produced by the action of gases on
trachytic and other lavas; the relation, however, of its origin to the
composition of lava is not yet well understood. Von Buch says that it
never occurs where only Labrador-felspar is present.

Lava.—This term has a somewhat vague signification, having been

applied to all melted matter observed to flow in streams from
volcanic vents. When this matter consolidates in the open air, the
upper part is usually scoriaceous, and the mass becomes more and
more stony as we descend, or in proportion as it has consolidated
more slowly and under greater pressure. At the bottom, however, of
a stream of lava, a small portion of scoriaceous rock very frequently
occurs, formed by the first thin sheet of liquid matter, which often
precedes the main current, or in consequence of the contact with
water in or upon the damp soil.

The more compact lavas are often porphyritic, but even the
scoriaceous part sometimes contains imperfect crystals, which have
been derived from some older rocks, in which the crystals pre-
existed, but were not melted, as being more infusible in their nature.

Although melted matter rising in a crater, and even that which

enters rents on the side of a crater, is called lava, yet this term
belongs more properly to that which has flowed either in the open
air or on the bed of a lake or sea. If the same fluid has not reached
the surface, but has been merely injected into fissures below
ground, it is called trap.

There is every variety of composition in lavas; some are trachytic,

as in the Peak of Teneriffe; a great number are basaltic, as in
Vesuvius and Auvergne; others are andesitic, as those of Chili; some
of the most modern in Vesuvius consist of green augite, and many of
those of Etna of augite and Labrador-felspar.[374-A]

Trap tuff, volcanic tuff.—Small angular fragments of the scoriæ

and pumice, above mentioned, and the dust of the same, produced
by volcanic explosions, form the tuffs which abound in all regions of
active volcanos, where showers of these materials, together with
small pieces of other rocks ejected from the crater, fall down upon
the land or into the sea. Here they often become mingled with
shells, and are stratified. Such tuffs are sometimes bound together
by a calcareous cement, and form a stone susceptible of a beautiful
polish. But even when little or no lime is present, there is a great
tendency in the materials of ordinary tuffs to cohere together.

Besides the peculiarity of their composition, some tuffs, or volcanic

grits, as they have been termed, differ from ordinary sandstones by
the angularity of their grains. When the fragments are coarse, the
rock is styled a volcanic breccia. Tufaceous conglomerates result
from the intermixture of rolled fragments or pebbles of volcanic and
other rocks with tuff.

According to Mr. Scrope, the Italian geologists confine the term

tuff, or tufa, to felspathose mixtures, and those composed principally
of pumice, using the term peperino for the basaltic tuffs.[374-B] The
peperinos thus distinguished are usually brown, and the tuffs grey or
white.

We meet occasionally with extremely compact beds of volcanic

materials, interstratified with fossiliferous rocks. These may
sometimes be tuffs, although their density or compactness is such as
to cause them to resemble many of those kinds of trap which are
found in ordinary dikes. The chocolate-coloured mud, which was
poured for weeks out of the crater of Graham's Island, in the
Mediterranean, in 1831, must, when unmixed with other materials,
have constituted a stone heavier than granite. Each cubic inch of the
impalpable powder which has fallen for days through the
atmosphere, during some modern eruptions, has been found to
weigh, without being compressed, as much as ordinary trap rocks,
and to be often identical with these in mineral composition.

The fusibility of the igneous rocks generally exceeds that of other

rocks, for there is much alkaline matter and lime in their
composition, which serves as a flux to the large quantity of silica,
which would be otherwise so refractory an ingredient.

It is remarkable that, notwithstanding the abundance of this silica,

quartz, that is, crystalline silica, is usually wanting in the volcanic
rocks, or is present only as an occasional mineral, like mica. The
elements of mica, as of quartz, occur in lava and trap; but the
circumstances under which these rocks are formed are evidently
unfavourable to the development of mica and quartz, minerals so
characteristic of the hypogene formations.

It would be tedious to enumerate all the varieties of trap and lava

which have been regarded by different observers as sufficiently
abundant to deserve distinct names, especially as each investigator
is too apt to exaggerate the importance of local varieties which
happen to prevail in districts best known to him. It will be useful,
however, to subjoin here, in the form of a glossary, an alphabetical
list of the names and synonyms most commonly in use, with brief
explanations, to which I have added a table of the analysis of the
simple minerals most abundant in the volcanic and hypogene rocks.
 Explanation of the names, synonyms, and mineral
composition of the more abundant volcanic rocks.

Amphibolite. See Hornblende rock, amphibole being Haüy's name for

hornblende.
Amygdaloid. A particular form of volcanic rock; see p. 372.
Augite rock. A kind of basalt or greenstone, composed wholly or
principally of granular augite. (Leonhard's Mineralreich, 2d
edition, p. 85.)
Augitic-porphyry. Crystals of Labrador-felspar and of augite, in a
green or dark grey base. (Rose, Ann. des Mines, tom. 8. p.
22. 1835.)

Basalt. Chiefly augite—an intimate mixture of augite and felspar with

magnetic iron, olivine, &c. See p. 371. The yellowish green
mineral called olivine, can easily be distinguished from
yellowish felspar by its infusibility, and having no cleavage.
The edges turn brown in the flame of the blow-pipe.
Basanite. Name given by Alex. Brongniart to a rock, having a base of
basalt, with more or less distinct crystals of augite
disseminated through it.

Claystone and Claystone-porphyry. An earthy and compact stone,

usually of a purplish colour, like an indurated clay; passes into
hornstone; generally contains scattered crystals of felspar and
sometimes of quartz.
Clinkstone. Syn. Phonolite, fissile Petrosilex; a greenish or greyish
rock, having a tendency to divide into slabs and columns;
hard, with clean fracture, ringing under the hammer;
principally composed of compact felspar, and, according to
Gmelin, of felspar and mesotype. (Leonhard, Mineralreich, p.
102.) A rock much resembling clinkstone, and called by some
Petrosilex, contains a considerable percentage of quartz and
felspar. As both trachyte and basalt pass into clinkstone, the
rock so called must be very various in composition.
Compact Felspar, which has also been called Petrosilex; the rock so
called includes the hornstone of some mineralogists, is allied
to clinkstone, but is harder, more compact, and translucent. It
is a varying rock, of which the chemical composition is not
well defined, and is perhaps the same as that of clay.
(MacCulloch's Classification of Rocks, p. 481.) Dr. MacCulloch
says, that it contains both potash and soda.
Cornean. A variety of claystone allied to hornstone. A fine
homogeneous paste, supposed to consist of an aggregate of
felspar, quartz, and hornblende, with occasionally epidote,
and perhaps chlorite; it passes into compact felspar and
hornstone. (De la Beche, Geol. Trans. second series, vol. 2. p.
3.)

Diallage rock. Syn. Euphotide, Gabbro, and some Ophiolites.

Compounded of felspar and diallage, sometimes with the
addition of serpentine, or mica, or quartz. (MacCulloch. ibid.
p. 648.)
Diorite. A kind of greenstone, which see. Components, felspar and
hornblende in grains. According to Rose, Ann. des Mines,
tom. 8. p. 4., diorite consists of albite and hornblende.
Dioritic-porphyry. A porphyritic greenstone, composed of crystals of
albite and hornblende, in a greenish or blackish base. (Rose,
ibid. p. 10.)
Dolerite. Formerly defined as a synonym of greenstone, which see.
But, according to Rose (ibid. p. 32.), its composition is black
augite and Labrador-felspar; according to Leonhard
(Mineralreich, &c. p. 77.), augite, Labrador-felspar, and
magnetic iron.
Domite. An earthy trachyte, found in the Puy de Dome, in Auvergne.

Euphotide. A mixture of grains of Labrador-felspar and diallage.

(Rose, ibid. p. 19.) According to some, this rock is defined to
be a mixture of augite or hornblende, and saussurite, a
mineral allied to jade. (Allan's Mineralogy, p. 158.) See
Diallage rock.
Felspar-porphyry. Syn. Hornstone-porphyry; a base of felspar, with
crystals of felspar, and crystals and grains of quartz. See also
Hornstone.

Gabbro, see Diallage rock.

Greenstone. Syn. Dolerite and diorite; components, hornblende and
felspar, or augite and felspar in grains. See above, p. 372.
Greystone. (Graustein of Werner.) Lead grey and greenish rock,
composed of felspar and augite, the felspar being more than
seventy-five per cent. (Scrope, Journ. of Sci. No. 42. p. 221.)
Greystone lavas are intermediate in composition between
basaltic and trachytic lavas.

Hornblende Rock. A greenstone, composed principally of granular

hornblende, or augite. (Leonhard, Mineralreich, &c., p. 85.)
Hornstone, Hornstone-porphyry. A kind of felspar porphyry (Leonhard,
ibid.), with a base of hornstone, a mineral approaching near
to flint, differing from compact felspar in being infusible.
Hypersthene Rock, a mixture of grains of Labrador-felspar and
hypersthene (Rose, Ann. des Mines, tom. 8. p. 13.), having
the structure of syenite or granite; abundant among the traps
of Skye. Some geologists consider it a greenstone, in which
hypersthene replaces hornblende.

Laterite. A red jaspery rock, composed of silicate of alumina and

oxide of iron. Abundant in the Deccan, in India; and referred
to the trap formation; from Later, a brick or tile.

Melaphyre. A variety of black porphyry, the base being black augite

with crystals of felspar; from μελας, melas, black.

Obsidian. Vitreous lava like melted glass, nearly allied to pitchstone.

Ophiolite, sometimes same as Diallage rocks (Leonhard, p. 77.);
sometimes a kind of serpentine.
Ophite. A green porphyritic rock composed chiefly of hornblende,
with crystals of that mineral in a base of the same, mixed
 with some felspar. It passes into serpentine by a mixture of
talc. (Burat's d'Aubuisson, tom. ii. p. 63.)

Pearlstone. A volcanic rock, having the lustre of mother of pearl;

usually having a nodular structure; intimately related to
obsidian, but less glassy.
Peperino. A form of volcanic tuff, composed of basaltic scoriæ. See p.
374.
Petrosilex. See Clinkstone and Compact Felspar.
Phonolite. Syn. of Clinkstone, which see.
Pitchstone. Vitreous lava, less glassy than obsidian; a blackish green
rock resembling glass, having a resinous lustre and
appearance of pitch; composition various, usually felspar and
augite; passes into basalt; occurs in veins, and in Arran forms
a dike thirty feet wide, cutting through sandstone; forms the
outer walls of some basaltic dikes.
Porphyry. Any rock in which detached crystals of felspar, or of one or
more minerals, are diffused through a base. See p. 372.
Pozzolana. A kind of tuff. See p. 36.
Pumice. A light, spongy, fibrous form of trachyte. See p. 373.
Pyroxenic-porphyry, same as augitic-porphyry, pyroxene being Haüy's
name for augite.

Scoriæ. Syn. volcanic cinders; reddish brown or black porous form of

lava. See p. 373.
Serpentine. A greenish rock, in which there is much magnesia; usually
contains diallage, which is nearly allied to the simple mineral
called serpentine. Occurs sometimes, though rarely, in dikes,
altering the contiguous strata; is indifferently a member of
the trappean or hypogene series.
Syenitic-greenstone; composition, crystals or grains of felspar and
hornblende. See p. 372.

Tephrine, synonymous with lava. Name proposed by Alex. Brongniart.

Toadstone. A local name in Derbyshire for a kind of wacké, which
see.
Trachyte. Chiefly composed of glassy felspar, with crystals of glassy
felspar. See p. 372.
Trap tuff. See p. 374.
Trass. A kind of tuff or mud poured out by lake craters during
eruptions; common in the Eifel, in Germany.
Tufaceous Conglomerate. See p. 374.
Tuff. Syn. Trap-tuff, volcanic tuff. See p. 374.

Vitreous lava. See Pitchstone and Obsidian.

Volcanic Tuff. See p. 374.

Wacké. A soft and earthy variety of trap, having an argillaceous

aspect. It resembles indurated clay, and when scratched
exhibits a shining streak.
Whinstone. A Scotch provincial term for greenstone and other hard
trap rocks.

ANALYSIS OF MINERALS MOST ABUNDANT IN THE

VOLCANIC AND HYPOGENE ROCKS.

Alumin Magne Potash Iron Mangan Remain

Silica. Lime. Soda.
a. sia. . Oxide. ese. der.
Actinolite
(Bergman 64· — 22· — — — 3· — —
)
a
Albite 68·8 20·5 9·1
— trac — — — —
(Rose) 4 3 2
e
——
(mean of 69·4 19·4 0·2 9·9 a a
0·13 — —
4 5 4 2 5 trace trace
analyses)
Augite 53·3 22· 17·3
— 4·99 — — 0·09 —
(Rose) 6 19 8
——
(mean of 53·5 11·2 20· 10·7
1· — — 0·67 —
4 7 6 9 5
analyses)
Carbonat
56· 43·05
e of Lime — — — — — — —
33 C.
(Biot)
Chiastolit
e 68·4 30·1 0·27
4·12 — — — 2·7 —
(Landgra 9 7 W.
be)
Chlorite
(Vauqueli 26· 18·5 8· — — 2· 43· — —
n)
——
(mean of 27·4 14·5 0·5 30·6 6·92
17·9 1·56 — —
3 3 6 0 3 W.
analyses)
Diallage
60· — 27·5 — — — 10·5 — —
(Klaproth)
——
(mean of 43·3 26·4 5·5 11·5 8·54
2·2 — — —
3 3 1 8 3 W.
analyses)
Epidote
(Vauqueli 37· 21· — 15· — — 24· 1·5 —
n)
Felspar,
62·8 17·0
common — 3· 13· — 1· — —
3 2
(Vauq.)
—— 66·7 1·2
17·5 — 12· — 0·75 — —
(Rose) 5 5
—— 64·0 18·9 — 0·7 13·6 — 0·74 — —
(mean of 4 4 6 6
7
analyses)
Garnet 35·7 27·2
— — — — 36· 0·25 —
(Klaproth) 5 5
——
43· 16· — 20· — — 16· — —
(Phillips)
Hornblen a
42· 12· 2·25 11· — 30· 0·25 —
de (Klap.) trace
——
45·6 12·1 18·7 13·
(Bonsdorf — — 7·32 0·22 1·5 F.
9 8 9 85
f.)
Hypersth
54·2 a
ene 2·25 14· 1·5 — — 24·5 1· W.
5 trace
(Klaproth)
Labrador-
55·7 0·5
felspar 26·5 — 11· — 4· 1·25 —
5 W.
(Klap.)
Leucite 53·7 24·6 21·3
— — — — — —
(Klap.) 5 2 5
Mesotype 54·6 19·7 1·6 15· 9·83
— — — —
(Gehlen) 4 0 1 09 W.
Mica
42·5 11·5 9· — 10· — 22· 2· —
(Klaproth)
——
1·3
(Vauqueli 50· 35· — — — 7· — —
3
n)
——
(mean of 45·8 22·5 11·0
— — — 14· 1·45 —
3 3 8 8
analyses)
Olivine
50· — 38·5 — — — 12· — —
(Klaproth)
Schorl or 35·4 34·7 4·68 — 0·48 1·7 17·4 1·89 4·02
Tourmalin 8 5 5 4 B.
 e
(Gmelin)
——
(mean of 36·0 35·8 0·2 1·9 13·7
4·44 0·71 1·62 —
6 3 2 8 6 1
analyses)
Serpentin
43·0 40·3 12·45
e 0·25 0·5 — — 1·17 —
7 7 W.
(Hisinger)
——
(mean of 37·2 2·8 12·77
4·97 36·8 — — 3·14 —
5 9 9 W.
analyses)
Steatite
(Vauqueli 64· — 22· — — — 3· — 5· W.
n)
——
(mean of 26·6 9·5
48·3 6·18 — — — 2· —
3 anal. by 5 W.
Klap.)
Talc. 61·7
— 30·5 — 2·75 — 2·5 — —
(Klaproth) 5

In the last column of the above Table, the letters B. C. F. W. represent Boracic acid,
Carbonic acid, Fluoric acid, and Water.