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would not be unadvisable, were it in strict con-
formity with nature. But there are many rocks
of this kind ; as, for example, the celebrated
Egyptian bricia, in which the fragments are
partly round and partly angular*; while the
term glutenite is liable to no such objections,
and the several structures identify the various
substances. t
English The celebrated English pudding-stone, found

pudding-stone.

no where in the world but in Hertfordshire, ap-
pears to me to be rather an original rock, formed
in the manner of amygdalites, because the peb-
bles do not seeln to have been rolled by water,
which would have worn off the substances in
various directions ; while, on the contrary, the
white, black, brown, or red circlets, are always
entire, and parallel with the surface, like those
of agates. Pebbles therefore, instead of being
united to form such rocks, may, in many cir-
cumstances, proceed from their decomposition j

* So also the celebrated pudding-stone of England. See Ano-
malous Rocks,



MODE XVI. SIDEEOUS GLUTENITB. 137

the circumjacent sand also arising from the de-
composition of the cement.

Mountains or regions of real glutenite often, Site *-
however, accompany the skirts of extensive
chains of mountains, as on the north-west and
south-east sides of the Grampian mountains in
Scotland, in which instance the cement is affirm-
ed by many travellers to be ferruginous, or some-
times argillaceous. The largeness or minuteness
of the pebbles or particles cannot be said to alter
the nature of the substance ; so that a fine sand-
stone is also a glutenite, if viewed by the mi-
croscope. They may be divided into two struc-
tures : the large-grained, comprising bricias and
pudding-stones ; and the small-grained, or sand-
stones.



STRUCTURE I. LARGE-GRAINED GLUTENITES.

Siderous glutenite, or pudding-stone, from Dun-
stamage, in Scotland, where it forms romantic
rocks of a singularly abrupt appearance, in some
parts resembling walls. The kernels consist of
white quartz, with green or black trap, porphyries,
and basaltins.

Glutenite, from the south of the Grampians,
from Ayrshire, from Inglestone bridge, on the
road between Edinburgh and Lanark. But of



38 DOMAIN I. SIDEROU3.

these the cement is often siliceous, as in those at
the foot of the Alps, observed by Saussure. The
siderous glutenites commonly originate from the
decomposition of siderous rocks, which also afford-
ed the cement.

Glutenite, consisting of fragments of granite,
cemented by trap.

Siderous glutenite, or pudding-stone'bf the most
modern formation. This is formed around can-
nons, pistols, and other instruments of iron, by
the sand of the sea.

Glutenite of small quartz pebbles, in a red fer-
ruginous cement, found in the coal-mines near
Bristol, &e.

Basaltic bricia, from Arthur's Seat, near Edin-
burgh.

Porphyritic bricia (Linn, a Gmelin, 247), from
Dalecarlia in Sweden, and Saxony. Calton-hill,
Edinburgh ?

STRUCTURE II. SMALL-GRAINED.

Aspect 1. The most remarkable of the side-
rous sand-stones, is that celebrated by the German
geologists under the appellation, given by the
Rothetodt miners, of Rot he todt Hebrides, or the red and

hegendes.

dead layer , so called from its colour, and because
it is wholly unproductive, no minerals being found



MODE XVI. SIDEROUS GLUTENITE. 139

in or under it. This singular rock has been termed
semiprotolite by Mr. Kirwan, implying that it is
half primitive ; and he informs us that it is com-
monly found under coal, is micaceous, and con-
tains lumps of porphyry or granite. The grains
are generally quartz or keralite, the cement being
an irony clay, which imparts the colour.

But as the passage affords some curious Ger-
man learning on the subject, from books little
known in this country, it shall be presented entire,,

" Semiprot elites (Rot lie todt liegendes).

" These stones I call by this name, as being
partly of primeval, and partly of subsequent, ori-
gin: they consist of pebbles, or of fragments, or
of sand of primeval origin, compacted and ce-
mented by an argillaceous, or calcareous, or sili-
eeous cement, of posterior origin; hence they
generally form the lowest stratum that separates
primeval rocks and secondary strata. From their
composition, they come under the denomination
either of farcilites, brecias, or sand-stones. In
some places this sand has been accumulated into
vast heaps, so as to form mountains 6 or 700 feet
high, and then compacted by an adventitious ce-
ment. Of this sort are the mountains of Hertz-
berg and Kaulberg, near Ilefeld, in which the
sand is cemented by a ferruginous cement, and



]40 DOMAIN I. SIDEROUS.

contains fragments of porphyry, and also veins of
iron-stone, and manganese, and strata of coal, with
impressions of reeds, rushes, and other plants,
Lasius, 249 and 280. The red colour is evidently
from iron.

:< The semiprotolite of Wartburg, near Eisenach,
contains rounded lumps of granite and schistose
mica : "substances found in the neighbouring moun-
tains. The semiprotolite of Goldlauter consists
entirely of porphyry, as do the primeval moun-
tains of that district. That of Kiffhauserberg, in
Thuringia, contains rounded argillites from the
neighbouring mountains of the Hartz. Petrified
wood is found in this last, Voigt's Letters, 19,
20. According to Voigt, the semiprotolite found
under coal has a siliceous cement, and contains
few primitive stones; Lettres sur les Montagnes,
3 1 . Saussure made the same observation on those
which he found on the descent of Trient, which
interceded between the primary and secondary
mountains, 2 Sauss. 699- He even remarked
long before, that primeval and secondary rocks
were almost always separated by a sand-stone or
farcilite, 1 Sauss. 594. Where the secondary
strata are calcareous, the semiprotolite has a cal-
careous cement; see Lehm. 168. Semiprotolite
is always red, by reason of the ferruginous par-
ticles by which it is cemented; its diffusion or



MODE XVI. SIDEROUS GLUTENITE. 141

expansion is unequal, being frequently horizontal
or even, but sometimes depressed, and in other
instances much elevated. Most of the super-
imposed strata partake of this inequality, and are
its natural consequences. Hence the protuber-
ances and depressions, otherwise called moulds,
observed in them ; Charp. Saxony, 371. It rests
on granite, Ibid. 370, 371."*

Mr. Jameson informs us that in the Hartz it
rests on grauwack, and extends nearly round the
whole of the country; nay, through Saxony, Hessia,
Bohemia, Silesia, and Franconia. The red sand-
stone of the north of England, which is micaceous,
and often regularly schistose, so as to form pave-
ments, &c. seems also to belong to this formation.
As the substance is widely spread and highly re-
markable, the barbarous denomination may be
exchanged for that of Lasite, in honour of Lasius,
the celebrated describer of the Hartz, who has
ably illustrated this substance.

Lasite, of various kinds, from Germany, of
which there is a series at the College des Mines,
in Paris, where it was shown to me by Daubuisson.

The same, from the north of England, &c. &c.

* Kirwan Geol. Essays, 25(5.



142 DOMAIN I. S1DEROUS.'

Aspect 2. Ferruginous sand-stone, of a light
brown, with glandules and veins of a deeper
colour, from Mont Calvaire, near Paris, where it
is frequent in ferruginous sand, probably arising
from its decomposition.

A ferruginous sand-stone, mentioned by Mr.
Kirwan, afforded 19 parts of iron in the 100.
The EisensanderZj or iron sand-stone of the Ger-
mans, is of this kind, and is sometimes worked as
an ore of iron.

In the Vosges mountains the summits are often
of ferruginous sand-stone, resting on granite*.
Dietrich, as already mentioned, thinks that red
sand-stone is as primitive as granite itself.

* Dietrich, Sivry, &c. Saussure says, 699, that the dadlyer
of the Germans, or rather deadlayer, is a pudding-stone.





.
DOMAIN II

SILICEOUS.



SILEX, SILICA, OR SILICEOUS EARTH.

THIS earth derives its name from the
silex, or flint, in which it abounds. Some
also* denominate it quartzose earth, be-
cause it is perhaps more abundant in the
stone called quartz, which, when trans-
parent and crystallised, is styled rock crys-
tal. It so frequently occurs in the form



144



DOMAIN II. SILICEOUS.



of sand, which covers a great part of the
globe, either alone or mixed with clay, that
late chemists infer that such sand arises not
only from the decomposition of rocks, but
isoften a disturbed or hasty crystallisation
of silica*. This is further confirmed by the
circumstance that many primitive moun-
tains consist of granular quartz, of an arena-
ceous appearance, like agglutinated sand.

The stones now called siliceous, were
formerly denominated verifiable; because,
with an alkali, they may be melted into
glass; and the finest Venetian glass was
fabricated from quartz, by the Italians
called tarso^. Silica, like the other sim-
ple earths, is a fine white powder; but the
particles have a harsh feel, like minute
sand. Alone it is scarcely fusible; but
when newly precipitated, is soluble in 1000
parts of water.

* The purity of this term may be doubted. Alumina is ridicu-
lous, being the plural of alumen. In the fabrication of new words
grammatical precision ought always to be studied.

f In the Phil. Trans. 1683, Dr. Lister says tarse is the quartzose
sand of which the fine Venetian glass was made. The same inge-
nious author there proposes, p. 739, Mineral Maps of Counties, as
he calls them.



DOMAIN II. SILICEOUS. 145

Joined with iron, argil, and magnesia, it
constitutes the primitive and most import-
ant rocks, rising to the regions of perpetual
snow, and thus supplying unfailing aliment
to the great rivers that fertilise the earth.
When considered in these .mountains, in
sand, and in clay, it may be pronounced
the most abundant of all the earths : and
if iron form the nucleus, the shell of this
planet may be said to consist chiefly of
silex. It is suspected that it is coeval
and intimately connected with iron ; as the
aerolites or meteoric stones, and the large
masses of native iron, discovered in Siberia
and South America, contain abundance of
silex mixed with some magnesia*.

Siliceous substances generally strike fire
with steel ; and flint or quartz yields a pe-
culiar odour, supposed by some to arise
from a subtile substance wtich chemistry
has not been able to discover. A strong
phosphorescence is also produced by col-

* Chrysolite, a mixture of silex and magnesia, is always found in
native iron. The exclamation of Henkel is well known :

O silex! silex! qnae te raaterculagessit?
VOL. I. L



146 DOMAIN XI. SILICEOUS.



lision, so that, during Alpine hurricanes,
the torrents, rolling large fragments of rock,
present a singular scene of corruscation.



MODE I. QUARTZ.

Distinctive Texture, compact, generally uniform, some-
characters. . .

times granular, rarely laminar, in which torm

the lustre is generally dull.

Hardness, crystallic. Fracture, splintery, but
such as sometimes to resemble the conchoidal.
Fragments, very sharp.

Weight, granitose.

Lustre, glistening or shining, sometimes unc-
tuous. From transparent to opake.

Colour, generally white; sometimes brown,
grey, yellow, red, or black.

It sometimes composes entire mountains, and
abounds in those of granite, in which substance
it is seldom crystallised.

STRUCTURE I. COMPACT.

Aspect 1. Opake. A very common substance,

but the specimens of entire mountains are rare.

Sites. Th e mountain of Kultuck, on the south-west

end of the lake Baikal, 350 feet high, and 4800

long, and still broader, consists entirely of milk-



MODE 1. ftUARTZ. 147

white quartz: per Laxman, 1 Chy. An. 1785,
265. Also Flinzberg, in Lusatia, almost entirely.
2 Berg. Jour. 1789, 1054. There is also an ex-
tensive narrow ridge of quartz, some miles long,
in Bavaria. 2 Berg. Jour. 1790, 529, &c. Flurl
Bavaria, 309. Monnet mentions a rock of quartz
60 feet high. 17 Roz. 163. Mountains of it also
occur in Thuringia. Voigt Prack. 69- and in Si-
lesia. Gerh. Beytr. 87. and in Saxony. 1 Berg. '
Jour. 1788, 269. and in layers between gneiss
and slate mica. 2 Lenz. Also in Scotland. 2
Wms. 52. It is not metalliferous. Werner Kurse
Classif. 15. Petrol is often found in it. 1 Berg.
Jour. 1 79 1 , 9 1 . The mountain of S we tiaia Gora,
among the Uralian, consists of round grains of
quartz, white and transparent, and of the size of
a pea, united without any cement. 2 Herm. 278*."
Mountains of quartz also occur in Scotland,
where, from the white substance, they sometimes
appear as if covered with snow. A hill of this
kind is seen near Cullen, which supplies glass-
works at Newcastle with quartz. The mountains
of Scuraben and Morven, in Caithness, are chiefly
constituted of this substance ; which also, accord-
ing to Mr. Jameson, occurs in great quantity in
the islands of Hay, Jura, and Coll. There are
also large rocks of quartz in Upper Lorn. Buf-

* Kirwan Geol. Ess. 179.
L2



148 DOMAIN II. SILICEOUS.

fon says*, there is in Auvergne, near Salvert, a
vein of quartz 10,000 fathoms in length.

In the Uralian mountains it sometimes happens
that there is an entire mountain of quartz, another
of felspar, and a third of talc, thus presenting the
materials of granite on a very large scale.

Aspect 2. Semi-transparent. This sometimes
forms very extensive veins, but perhaps never con-
stitutes an entire hill or rock.

Aspect 3. Unctuous. This also appears in
veins, and generally accompanies metals.

STRUCTURE II. GRANULAR.

This kind often constitutes entire mountains in
Scotland, and other parts of the world. It has
sometimes been confounded with siliceous sand-
stone, but late writers have demonstrated that it
may be owing to a primitive but disturbed crystal-
lisation f. Nor is it inconsistent that where the
cement was deficient or interrupted, it should
appear among the most ancient substances in the
shape of mere sand. The grains, as already men-
tioned, are sometimes of the size of peas.

* Min. i. 100.

f Collate however the account of the Siliceous Sand-stones,
Mode XIV. Str. 2.



MODE I. QUARTZ.

Grey granular quartz, from Balahulish, in Scot-
land.

The same, with veins of white semi-transparent
quartz, from Bunessan, Mull.

Saussure describes, 999, rocks of a beautiful
granular quartz, which rises in leaves of a rhom-
boidal form. It is very hard, and has the grain
and whiteness of statuary marble.

He also observes, 2235, that in primitive lime-
stone there are often veins of quartz, as there are
also veins of keralite or hornstein in compact lime-
stone. Query, if both the latter substances do
not contain more argil ?

Mr. Playfair observes that granular quartz is
common in Scotland, alternating with schisti, par-
ticularly on the north side of the harbour of Bala-
hulish, and on the sea- shore at Cullen. He also
shows that sand is a crystallisation ; and mentions
a siliceous grit with no cement*.

In Buckinghamshire, Wiltshire, and Dorset-
shire, where there are only sand and chalk, there
is found in the sand a prodigious number of large
blocks of granular quartz, which is used for paving
or building. The castle of Windsor, and the ter-
race, are built of this stone, probably from the
forest, or the neighbouring heaths, where there is

* Hutt. Theory, 27, 1?1, &c.



150 DOMAIN II. SILICEOUS.

a great quantity; and Stonehenge is built of these
blocks. So blocks of granite are found in Bran-
denburg, Mecklenburg, and Pomerania*.

Mountains of granular quartz abound in Scot-
land ; and granitic mountains in Sweden. When
the continents were gradually emerging, and before
these large subsidences which form mediterranean
seas, it may easily be conceived that the plains
where such blocks, and gravel foreign to the sur-
rounding mountains, are always found, were co-
vered for ages by the waters of the ocean, which
rolled these blocks and gravel in the Direction of
their currents.

In a late volume of the Philosophical Trans-
actions t, Bournon gives some observations on the
different modes of attraction, which influence the
formation of minerals. The attractions of aggre-
gation are either simple or crystalline.

" It sometimes happens (owing perhaps to a
more considerable degree of disturbance during
the process of attraction), that there are found
small irregular detached masses, often so minute
as to be scarcely perceptible ; at other times they
are of a larger size, and, as soon as formed, fall to
the bottom of the liquor, and unite together by a

* De Luc, Geologic. Paris 180Q, 8vo. p. 332.
f 1804, p. 37.



MODE I. QUARTZ. 151

simple mode of attraction, which may with great
propriety be called simple homogeneous attraction
of aggregation. Of this kind are, granulated
quartz, granulated carbonate of lime, &c. the dif-
ferent kinds of which substances differ from each
other only by the fineness or coarseness of their
grain."

Sometimes this takes place along with the crys-
talline, whence small crystals, &c. Sometimes
the molecules are precipitated in a detached but
confused manner, so as to form earthy or compact
substances. In aggregate stones there is the
attraction of aggregation, as in granite, sand-
stone, and others.

But long before, Mr. Kirwan* had made the
following observations :

' The first step in the process of crystallisation
is the formation of grains ; the second is the in-
crease in one dimension ; the third in two dimen-
sions ; and the fourth in three dimensions : the
grains themselves, however, to be visible, must
receive accretions in the three dimensions. If the
process be uninterrupted, no traces of distinction
will be perceived, and the whole will appear per-
fectly uniform ; but, if it be disturbed in the first
step, no crystallisation can take place ; if in the

* Mia. i. 21, edit. 17p4



DOMAIN II. SILICEOUS.



second, the grains will appear distinct, small or
gross, coarse or fine, according to the nature of
the disturbance, whether by the interruption of the
process, or the accession of foreign matter ; this
latter generally produces coarse or rude grains, in
proportion to the quantity.

" If the disturbance only takes place in the
third stage, we shall have fibres or striae, as com-
plete surfaces cannot be formed ; the striae having
more extension in breadth than the fibres or fila-
ments, argue a smaller degree of disturbance than
the mere fibrous appearance.

" If, during the third stage, the striae be forced
into contact by the gradual dereliction of the fluid
that kept them suspended, they will form lamellae
in proportion as they are deserted, which will
either adhere to each other, and then fall con-
fusedly, being too heavy to be supported by the
menstruum, or, if supported, will be superimposed
on each other.

" But if the process of crystallisation be dis-
turbed only in the fourth stage, then the form and
shape only of the crystals will be more or less
altered.

" All these steps are noticed and described by
chemical writers; and particularly by the cele-
brated Rouelle, in the Memoirs of the Academy of
Paris on the crystallisation of salts."



MODE II. KERALITE. 153

STRUCTURE III. LAMINAR.

This is generally dull, and approaches to the
next Mode, keralite, or rock-flint. The layers are
commonly thin, that is, from a quarter of an inch
to an inch. It forms a hill near Bamf. Saussure,
1483, has described a black schistose quartz,
which may be a siliceous schistus of the Ger-
mans.

The cellular, stalactitic, fibrous, and other struc-
tures, seem to occur only in small portions, and
rather belong to lithology or gemmology.



MODE II. KERALITE, OR ROCK-FLINT.

Texture, compact and uniform, but sometimes characters,
laminar.

Hardness, crystallic. Fracture, splintery, con-
choidal : the scaly fracture distinguishes it from
flint. Fragments, sharp.

Weight, granitose; sometimes, but rarely, car-
bonose.

Lustre, dull. Opake; but often translucent
on the edges.

Colour, grey, black, green, &c. *

It composes entire mountains.

This rock is the hornstdn of the Qermans, Homstein,



]54 DOMAIN 11. SILICEOUS.

Petrosiiex. an( ] the petrosil&v of their writers in Latin ; which
has of course been confounded with the petro-
silex of the Swedes and French, which is com-
pact felspar. To avoid this confusion the Greek
term keralite has been adopted, from Lametherie.
Keralite is not fusible by the blow-pipe, but
compact felspar generally is. It is also often
found impregnated with metals, while compact
felspar or felsite has perhaps never been observed
to attend metals. Felsite also presents the va-
rious colours of felspar; while keralite chiefly
passes from white, through grey, to black. It
may be regarded as an impure quartz, and
shares the sites and properties of that substance.
In England it is called chert, and often runs
in veins- or layers through lime-stone, particu-
larly in Derbyshire.

STRUCTURE I. MASSIVE*

Aspect 1. Common. Bluish grey rock-flint,
sometimes mamellated, and approaching to chal-
> cedony, from the lead-mines of Bretagne. This

is properly a vein-stone ; and Brongniart has ob-
served, i. 355, that such are hornsteim, though the
appearance be waxy, as they are infusible. Fel-
spar or felsite rarely appear as vein-stones.

Of a lighter grey, with blende and galena, frpm
the same.



MODE II. KERALITE. 1J5

With different laminar shades of black, but not
with a laminar fracture, from Giromagny in the
Vosges mountains, France*.

Interspersed with native silver, from the famous
mountain of Schlangenberg, or Zmeof, in the south
of Siberia, which seems entirely to consist of rock-
flint, mixed with silver.

From the great oriental chain of mountains in
Siberia, where, according to Patrin, it underlays
the ribbon jasper.

With crystals of felspar it forms what Werner
styles horns tone porphyry, for which see the Si-
liceous Intrites.

Aspect 2. Unctuous. There is also an unc-
tuous keralite, like what is called fat quartz. It
is sometimes mistaken for felsite.

STRUCTURE II. LAMINAR.

Aspect 1. The siliceous schistus of Werner, a
term very vague, as there are so many schisti of a
siliceous nature, is by Mr. Kirwan and others re-
garded as a schistose hornstone. It is a primitive
rock, usually of a greyish black, intersected with

* In another work the author has said that, in the ancient
phraseology, forests and mountains were often confounded. Roeslin
de Sylva Vasgovia (that is, an account of the mountains of Wasgaw,
or Vosges) is a modern example,



156 DOMAIN II. SILICEOUS.

small veins of white quartz. Of this the basanite,
or Lydian stone of Werner, is accounted only a
diversity ; but many regard it as a black jasper,
and as all the jaspers are impregnated with iron,
it would be truly surprising if there were no black
jasper. According to Mr. Jameson, the flinty
slate of Werner not only occurs in considerable
beds in primitive slate, but also, like quartz, forms
entire mountains.

It appears by the French writers to have been
sometimes confounded with a fine trap or basalt.
Latterly siliceous schistus has been understood to
present various colours; and when it occurs in
grauwacke slate, is regarded as a transitive rock.
The primitive is said to underlay the granite of
Mount Sorel, in Leicestershire.

chert. Aspect 2. The chert of the English* chiefly

occurs in layers in lime-stone, and sometimes con-
stitutes a mass of petrified shells.

Dark grey chert, with lime-stone, in layers,
from Derbyshire.

Reddish chert, with lime-stone, from France.

Brown chert, full of petrified shells, from Der-
byshire.

In bowls, with concentric layers, brown and
grey, from Vaucluse. Saussure, 1546.

* Chertz of some counties, which seems related to quartz.



DOMAIN II. SILICEOUS. 157



MODE III. FELSPAR. ;

Texture, strait, foliated. Characters.

Hardness, of course felsparic. Fracture, la-
minar. Cross fracture, fine-grained, uneven,
approaching the splintery. Fragments, sharp,
rather rhomboidal.

Weight, granitose.

External lustre, shining ; of the cross fracture,
glimmering, glassy, sometimes pearly. Trans-
lucent.

Colour, many varieties of white, grey, green,
and red ; rarely blue or black.

It often composes mountains, especially when
interspersed with mica; and is the most abundant
substance in granite, where it often forms distinct
crystals *.

There are mountains and large strata of fel-



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