and by others as a kind of opal (102). They are sometimes found in
Hanover, but are chiefly brought from the island of Ceylon. It is usual
to cut them before they are exported, and generally in a convex and
oblong form, without facets, and in such manner as to bring the streak
which intersects them into the centre. Among the king of Candy’s jewels,
which were sold by auction in London, in June 1820, was a cat’s─eye of
extraordinary magnitude and beauty. It was two inches in diameter, of
dark colour, and nearly hemispherical. This stone was set in gold, with
small rubies round it, and was sold for more than 400_l._
Cat’s─eyes are chiefly used for setting in rings. Their size seldom
exceeds that of a hazel nut; but there was one in the cabinet of the
Dukes of Tuscany, which was nearly an inch in diameter. Those that are
the most highly esteemed are of an olive─green, or red colour.
87. _WOODSTONE is a very hard mineral substance, supposed to have been
wood petrified with a siliceous mineral called hornstone._
_It is of various colours; and has not only the external appearance, but
the internal organization of wood._
This extraordinary mineral is found embedded in sandy loam, in alluvial
soil (269), and occurs in various parts both of Europe and Asia. It has
been found in ferruginous sand, near Woburn, in Bedfordshire, and near
Nutfield, in Surrey. Immense pieces of it are discovered in some places
in the original shape of the trees; trunks, branches, and roots. In the
year 1752 the whole under part of the trunk of a tree, with its branches
and roots, was found, in a state of woodstone, near Chemnitz, in Saxony;
and, in the Electoral Cabinet at Dresden, there is part of the trunk of
a tree, from the same place, which measures five feet in length and as
many in thickness.
Woodstone is in considerable request by lapidaries. It takes a good
polish, and is made into beads for necklaces, and other female
ornaments. In the East Indies it is generally called _Petrified Tamarind
Tree_.
88. _COMMON SAND is a granulated kind of quartz; or consists of rounded
grains of small size, which have a vitreous or glassy surface._
_It is usually of white or yellowish colour; but is sometimes blue,
violet, or black._
In the torrid regions of Africa and Asia there are immense tracts of
desert covered only with sand, so dry and light as to be moveable before
the wind, and to be formed into vast hills and boundless plains. These
are incessantly changing their place, and frequently overwhelm and
destroy the travellers whose necessities require them to enter these
dreary realms.
Sand has numerous uses. When mixed in due proportion with lime, it forms
that hard and valuable cement called mortar. Melted with soda (200) and
potash (205) it is formed into glass; white sand being used for the
finer kinds, and coarse and more impure sand for bottle glass. A very
pure kind of sand which is found in Alum Bay, on the west side of the
Isle of Wight, and on some parts of the coasts of Norfolk, is in great
request by glass─makers. Sand is also employed in the manufacture of
earthenware; and its utility in various branches of domestic economy,
but particularly for the scouring and cleaning of kitchen utensils, is
well known. In agriculture sand is used by way of manure, to all soils
of clayey lands: as it renders the soil more loose and open than it
would otherwise be. The best sand for this purpose is that which is
washed by rains from roads or hills, or that which is taken from the
beds of rivers.
There is a kind of sand which is naturally mixed with clay, and has the
name of _Founder’s Sand_, from its being chiefly employed in the
formation of moulds to cast metals in. At Neuilly, in France, there is a
bed of perfectly transparent and crystalline sand. Each grain, when
examined with a magnifying glass, is seen to consist of a perfect
six─sided prism, terminated by two six─sided pyramids.
The uses of the different kinds of _Sandstone_ will be enumerated in the
account of the rocks (267, 268).
89. _LYDIAN STONE is a kind of flinty─slate, of greyish or velvet─black
colour, not quite so hard as flint, opaque, and about twice and a half
as heavy as water._
_It is usually massive, and, internally, has a glimmering appearance._
This mineral occurs in beds in primitive clay─slate (257); and is found
in Bohemia and Saxony, and also in the Pentland hills near Edinburgh. It
was first noticed in Lydia, whence it derived its name.
It is sometimes used as a touchstone to ascertain the purity of gold and
silver. This was its use among the ancients. The metal to be examined is
drawn along the stone so as to leave a mark, and its purity is judged by
the colour of the metallic streak. A good touchstone should be harder
than the metals, or metallic compounds to be examined; if softer, the
powder of the stone mixes with the trace of the metal and obscures it. A
certain degree of roughness on the surface of the best stone is also
requisite, that the metal to be tried may leave a trace or streak
sufficiently distinct. It must not, however, be too rough, otherwise the
particles of the metal will be hid amongst its inequalities, and no
distinct trace will be formed. The touchstone should also be of black
colour, as this tint shows the colour of the streak better than any
other.
90. _FLINT is a peculiarly hard and compact kind of stone, generally of
smoke─grey colour, passing into greyish white, reddish, or brown. It is
nearly thrice as heavy as water, and when broken will split, in every
direction, into pieces which have a smooth surface._
_It is very common in several parts of England, generally among chalk,
arranged in a kind of strata or beds, and in pieces that are for the
most part either rounded or tubercular._
The property which flint possesses of yielding sparks, when struck
against steel, has rendered it an article of indispensable utility in
the system of modern warfare. To this substance the sportsman also is
indebted for a means of obtaining his game. The art of cutting, or
rather of breaking, this stone into gun─flints is of modern date, and
was for a long time kept secret. The most absurd and contradictory
accounts have been given of it by various writers; and it is only of
late that the true mode has been rendered public. It consists in
striking the stone repeatedly with a kind of mallet, and bringing off at
each stroke a splinter which is sharp at one end and thick at the other.
These splinters are afterwards shaped, by placing them upon a sharp iron
instrument, and then giving them repeatedly small blows with a mallet.
During the whole operation the workman holds the stone in his hand, or
merely supports it on his knee: and the operation is so simple, that a
good workman has no difficulty in making 1500 flints in a day. The
manufacture of gun─flints is chiefly confined to England, and two or
three departments in France. In Prussia an attempt was once made to
substitute a kind of earthenware or porcelain for flint; and such was,
for some time, used by the Prussian soldiers. All the kinds of flint are
not equally adapted for guns: the best are the yellowish grey; the dark
smoke and ash─grey varieties are also used, but they are neither so easy
to be split, nor do they afford such thin fragments as the other; and,
owing to their greater hardness, they wear the lock sooner.
Flint is employed in the manufacture of porcelain and glass. For this
purpose it is heated red hot, and, in that state, is thrown into cold
water. It is then of a white colour, and capable, without difficulty, of
being reduced to powder, either in a mortar or by a mill. After this
powder has been passed through fine sieves, some aqua fortis is poured
upon it, to dissolve any particles of iron which it may have acquired in
the grinding. The powder is then several times washed in hot water, and
afterwards dried for use. The glass that is manufactured from this
substance is perfectly transparent and faultless.
_Glass_ is made by mixing sand, or prepared flint, with a certain
proportion of soda (200) or potash (205); and exposing these substances,
in a furnace, to a violent heat. When they are in a perfectly fluid
state, part of the melted matter is taken out at the end of a long
hollow tube. This is done by dipping the tube into it, and turning it
about until a sufficient quantity is taken up; the workman, at each
turn, rolling it gently upon a piece of iron, to unite it more
intimately. He then blows through the tube till the melted mass, at the
extremity, swells like a bubble; after which he rolls it again on a
smooth surface to polish it, and repeats the blowing until the glass is
brought as nearly to the size and form of the vessel required, as he
thinks necessary.
If he be forming a common bottle, the melted matter at the end of the
tube is put into a mould of the exact size and shape of the body of a
bottle; and the neck is formed by drawing out the ductile glass at the
upper extremity.
If he be making a vessel with a large or wide orifice, the glass, in its
melted state, is opened and widened with an iron tool; after which,
being again heated, it is whirled about with a circular motion, and, by
the centrifugal force thus produced, is extended to the size required.
Should a handle, foot, or any thing of similar kind be required, that is
made separately, and stuck on in its melted state.
_Window glass_ is made in a similar manner, except that the mass at the
end of a tube is formed into a cylindrical shape. This being cut
longitudinally by scissars or shears, is gradually bent back until it
becomes a flat plate.
Large _plate glass_ for looking─glasses is made by suffering the mass,
in a state of complete fusion, to flow upon a casting table, with iron
ledges. These confine the melted matter, and, as it cools, a metallic
roller is passed over it, to reduce it to an uniform thickness.
Glass utensils, unless very small and thin, require to be gradually
cooled in an oven. This operation is called _annealing_, and is
necessary in order to prevent them from cracking by change of
temperature, wiping, or slight accidental scratches.
It appears that the manufacture of glass was known very early; but glass
perfectly transparent was esteemed of extremely high value. It is stated
that the Emperor Nero purchased two glass cups with handles for a sum
which was equivalent to 50,000_l._ of our money. The windows of some of
the houses of the ancient city of Pompeii, which was buried by an
eruption of Mount Vesuvius, in the year 79, were glazed, but the glass
was thick, and not transparent.
By many persons flint is used as a test for ascertaining the purity of
silver coins. This is done by rubbing them upon the flint; and if the
mark which they leave be not perfectly white, they are rejected as
counterfeit.
91. _CALCEDONY is a species of quartz, generally of whitish, bluish, or
smoke─grey colour; and, when broken, it appears internally dull, and
somewhat splintery._
_It is generally found in a massive state, is harder than flint,
generally semi─transparent, and 2½ times heavier than water._
The name of this stone is derived from Chalcedon, in Upper Asia, whence
it appears to have been originally obtained, and where it is still found
in considerable abundance. Several superb specimens of calcedony have
been found in Britain, and particularly in some of the tin and copper
mines of Cornwall. It occurs in several parts of Scotland; and in many
of the countries of the Continent. In the Leverian Museum there was a
specimen of calcedony, which weighed more than 200 pounds. Its whole
surface appeared such that, at first sight, one might imagine it to have
formerly been in a liquid state: it had much the appearance that thick
oil has while boiling.
Few stones are susceptible of a higher or more beautiful polish than
calcedony. Hence the different varieties of it are cut into ring and
seal stones, necklaces, ear─pendants, small vases, cups, and
snuff─boxes.
92. _ONYX is a kind of calcedony, generally marked alternately with
stripes of white and black, or white and brown._
Its name is derived from the Greek language, and has been given on
account of its resemblance in colour to the whitish band at the base of
the human nail. The distinction which appears to be made betwixt onyx
and _sardonyx_, arises from the colours of the former being arranged
either concentrically, or in a somewhat confused manner, and those of
the latter in regular stripes or bands.
Both these kinds are highly esteemed by lapidaries, for the formation of
vases, snuff boxes, and trinkets of various kinds. Of sardonyx the
ancients made those beautiful cameos, many of which still ornament our
cabinets. The ingenuity they have shown, in the accommodation of the
natural veins and marks of the stone to the figures engraven upon them,
is such as to excite, in many instances, the greatest admiration.
It is said that we are entirely ignorant of the country whence the
ancient artists obtained the large specimens of sardonyx which are now
found in some cabinets.
Onyx is imported from the East Indies, Siberia, Germany, and Portugal.
93. _CARNELIAN is another kind of calcedony usually of a red or flesh
colour, though sometimes white, orange, or yellow._
On several of the British shores carnelians are found with other
pebbles: but the most beautiful and valuable kinds are imported from the
East Indies. These are sometimes so large as to measure nearly three
inches in diameter. The kinds principally in request are those of pure
white, and bright red colour; and jewellers have the art of changing the
colour of the yellow varieties to red, by heat.
No stone is so much in request for seals as carnelian. It is likewise
cut into beads for necklaces, and stones for ear─rings; into crosses,
bracelets, and other trinkets, which, in India, form a considerable
branch of traffic. The amount of the sale value of different kinds of
carnelian goods vended by the East India Company in 1807, was
11,187_l._: but, in other years, it has not usually been so much as half
that sum.
Formerly carnelians were exported from Japan to Holland; and thence were
carried to Oberstein, in France, to be exchanged for the agates of that
country, which were exported to China.
The carnelian was much esteemed by the ancients; and many fine engraved
carnelians are preserved in different collections.
94. _CHRYSOPRASE, an extremely hard kind of stone, of clear and delicate
apple─green colour, is considered to be a kind of calcedony._
This beautiful mineral has hitherto been found only in the vicinity of
Kosemitz, and in a few other parts of Lower Silesia. It is susceptible
of a high polish, and is much prized by jewellers when its colour is
deep and pure. Its colour, however, is so fugitive, that, if kept in a
warm and dry situation, it loses the greatest part of it; and if exposed
to moisture it becomes much altered. Lapidaries assert, that great care
ought to be taken in the polishing of it;—pretending that if, from want
of sufficient moisture, or by the too rapid motion of the wheel, it be
over─heated, it will become whitish or turbid.
Chrysoprase is generally cut into a convex form, or what jewellers call
_en cabochon_; and is set with green taffeta beneath it, as foil. It is
used for ring stones, brooches, and other ornaments; and is found to
harmonize well with diamonds and pearls. The larger and more impure
masses are cut into snuff─boxes, seal stones, and similar articles. Some
of the finest specimens of chrysoprase that are known, are to be seen in
the cathedral church of Prague, where a small closet is inlaid with
them.
Imitations of chrysoprase are sometimes imposed upon the public; but
these are easily known by persons who are acquainted with the nature of
precious stones.
95. _BLOODSTONE, or HELIOTROPE, is an opaque stone of the quartz family,
generally of dark green colour, with a somewhat bluish cast, and marked
with blood─red spots or stripes._
_It usually occurs in masses of irregular form; and, when cut thin, is
sometimes translucent at the edges._
The most valuable kinds of bloodstone are imported from the East. They
are not so opaque as those which are found in Germany, and are marked
with more vivid spots. As bloodstone is capable of a high polish, and is
even better calculated for engraving upon than carnelian (93), it is in
great request for seal stones, for the tops and bottoms of snuff─boxes,
and other articles on which costly gold mountings are frequently
bestowed. Its dark colour and opaque appearance prevent its being much
used for beads. Great quantities of it are consumed in China as
ornaments to the girdle clasps of the superior ranks of people. Absurd
as it may appear, many persons entertain a notion that this stone worn
in the dress will prevent bleeding at the nose. Good bloodstone and
carnelian are considered to be about the same value.
There are many cameos and intaglios, both by ancients and moderns,
executed in bloodstone. In the National Library at Paris, there is a
fine engraved stone of this kind, representing the head of Christ whilst
undergoing the punishment of scourging, and so cut that the red spots
are made to represent drops of blood.
The ancients procured bloodstones chiefly from Ethiopia; but, at
present, the most highly esteemed varieties are brought from Bucharia,
Great Tartary, and Siberia. A kind of mineral nearly resembling this is
found in Rum, one of the western isles of Scotland.
The spots in bloodstone are particles of red jasper.
96. _JASPER is a species of quartz, and one of the hardest stones with
which we are acquainted. It varies much in colour, being red, green,
yellow, blue, olive, violet, black, and often variegated, spotted, or
veined with several other colours. It is usually opaque, but is capable
of receiving a beautiful polish._
_This stone is found in large and shapeless masses, and constitutes an
ingredient in mountains of various parts of the world._
Such is the hardness of jasper, that the savages of Canada avail
themselves of it for the fabrication of the heads of javelins, and
sometimes also of arrows. It is used by artists for the formation of
vases, snuff─boxes, seals, and trinkets of various kinds; and formerly
cups and saucers were sometimes made of it. Many beautiful antique
engravings have been made upon jasper.
In the province of Andalusia, in Spain, there are four fine quarries of
jasper. One of these is celebrated for a blood─red stone, streaked with
white, exceedingly hard and very handsome, of which the beautiful
columns of the tabernacle in the Escurial are made. This quarry is in
the territory of Cogullus, in the archbishopric of Seville, and was
purchased by the Crown in 1581; but was afterwards so far neglected that
even the place where it lay was not remembered. It was, however, again
discovered about the end of the reign of Charles the Third, after a very
expensive search made by order of the government.
Jasper occurs in the Pentland hills, near Edinburgh, and in several
other parts of Scotland; in the Shetland Islands, and Hebrides. It has
been observed in most of the countries of the Continent; and is found,
in great abundance, in Siberia.
97. RED JASPER _is an opaque red stone which is found embedded in red
clay─ironstone in Baden_; and is cut and polished for various ornamental
purposes. There are extant many fine antique engravings on red jasper.
98. EGYPTIAN PEBBLE _is a kind of jasper, that is found in globular or
rounded pieces, and is distinguishable when cut or broken, by its
numerous colours, arranged in concentric stripes or layers_. It is
chiefly brought from Egypt; and, as it is capable of receiving a fine
polish, and when polished is very beautiful, it is manufactured into
several kinds of ornamental articles. From the great abundance in which
it is supplied, it is, however, much less valuable than carnelian (93).
The colours of the Egyptian pebble frequently assume very singular
forms. There was one in the Leverian Museum which exhibited, in the
centre, the resemblance of a pantaloon, or a man wearing a fool’s cap.
99. STRIPED, or RIBBON JASPER, _is marked with alternate stripes of
different colours_; and is found in Siberia, Saxony, and even in the
Pentland hills, near Edinburgh. It receives an excellent polish, and is
frequently cut into the tops and bottoms of snuff─boxes. The red and
green layers of jasper, being well defined and regular, this kind is
used for several purposes of ornament, particularly for cameos.
100. _AGATE, or AGATE JASPER, as some mineralogists denominate it, is a
semi─transparent stone of the quartz family, which is capable of
receiving a high and very beautiful polish._
_These stones are always found in a shapeless or massive form, and
nearly of all colours, except bright red and green._
The name of agate is derived from the river Achates, in Sicily, in the
vicinity of which these stones were obtained by the ancients in great
abundance. They are now found in several parts of Scotland; in Iceland,
Saxony, and Hungary; and they are occasionally brought into Europe from
China and the East Indies.
Agates are used in several kinds of ornamental work, and particularly
for necklaces and seals. They are occasionally made into cups, the
handles of knives and forks, hilts of swords and hangers, and the tops
and bottoms of snuff─boxes. The less ornamental kinds are manufactured
into small mortars, which are employed by enamellers and others, for
pounding such substances as are too hard to be reduced in any other way.
They are also made into instruments for grinding colours, and into
polishers for the glazing of linen. In the Electoral Cabinet at Dresden,
and the Ducal Cabinet in Brunswick, there are several elegant vases
formed of agate.
The most beautiful agates which our island produces are known by the
name of _Scots Pebbles_. These are found in various parts of Scotland,
but principally on the sea─shore, in the neighbourhood of Dunbar. _Agate
pebbles_ are found on several of the English shores, as those of
Suffolk, Dorset, Scotland, Wales, and Ireland; and sometimes even in
gravel pits. Many of them will bear cutting and polishing as well as the
best agates of foreign countries.
Agates are occasionally seen to be figured in very singular manner; but
this, in some instances at least, is suspected to be the work of art.
One is mentioned in the church of St. Mark, at Venice, which had the
representation of a king’s head surmounted by a diadem. On another, was
represented a man in the attitude of running. But the most remarkable of
all seems to have been one which contained a representation of the nine
Muses, with Apollo in the midst of them!
It must be remarked that agate is not, as some mineralogists imagine, a
simple mineral, but that it is composed of various species of the quartz
family, intimately blended together. It consists chiefly of calcedony
(91), with flint, hornstone, carnelian (93), jasper (96), cacholong
(105), amethyst (79), and quartz (76). Of these minerals sometimes only
two, and sometimes three or more, occur in the same agate. Its
varieties, consequently, are extremely numerous.
101. MOCHOA STONE _is a kind of agate, which has on its surface the
resemblance of moss_; and this so nearly approaching a natural
appearance, that some persons have actually supposed it to be occasioned
by a condensation of moss into stone. Its name is derived from _mocks_,
the German word for moss.
These stones are used for several ornamental purposes; and are not
unfrequently imitated, by spreading a solution of copper in nitric acid
or aqua fortis (30) over the surface of a plain agate, and then setting
a small iron nail on its head in the middle. The acid unites with the
iron, and deposits the copper in beautiful ramifications from the
centre. The nail must then be removed, and the surface carefully washed
by dipping the stone into warm water. Afterwards, on the application of
a moderate heat, the copper becomes black. As, however, the deposition
is merely superficial, it requires to be covered with glass, to preserve
it from injury.