Agate.

The fossils known under this name are all compound substances; and hence cannot have a particular place in any systematic arrangement. Werner, therefore, has placed them as a supplement to the species chalrecony, which forms a principal constituent part of them, and disposes them according to their colourdelineations, thus: 1. Fortification agate; 2. Landscape agate; 9. Ribbon agate; 4. Moss agate; 5. Tube agate; 6. Clouded agate; 7. Land agate; 8. Star agate; 9. Fragment agate; 10. Punctuated agate; 11. Petrifaction agate; 12. Coal agate; 13. Jasper agate. They are all compounded of chalcedony, cornelian, jasper, horn-stone, quartz, heliotrope, amethyst, indurated lithomarge, and opal, in different quantities and proportions, and are found in great abundance in Germany, France, England, Scotland, Ireland, and the East Indies.

The uses of agate are various. It is cut into vases, mortars, snuff-boxes, seals, handles to knives and for many other useful purposes. See AGATE and CHALCEDONIUM.

Twenty-sixth Species. Heliotrope.

The principal colour is intermediate between leek and dark celadon green, or mountain-green. It occurs massive, and in angular as well as rolled pieces. Internally the lustre is glistening, and is always resinous. It is commonly translucent in the edges; is easily frangible, hard, and not particularly heavy. Heliotrope is found in rocks belonging to the floetz trap formation, in Asia, Persia, Siberia, Saxony, and Iceland.

On account of its beautiful colour and its hardness, it is employed for nearly the same purposes as agate. See HELIOTROPE.

Twenty-seventh Species. Plasma.

The usual colour is intermediate between grass and leek-green, and of different degrees of intensity. It occurs in indeterminably angular pieces, which have a rough earthy crust. Internally, its lustre is glistening. It is intermediate between semitransparent and strongly translucent, hard, brittle, frangible without great difficulty, and not particularly heavy.

Hitherto, it has only been found among the ruins of Rome, and constituted a part of the ornamental dress of the ancient Romans.

Twenty-eighth Species. Chrysopras.

Its characteristic colour is apple-green, of all degrees of intensity. It is found massive in angular pieces, and in thick plates. Internally it is duil; the lustre intermediate between translucent and semitransparent. It is hard, not very difficultly frangiUle, nor particularly heavy; and is found along with quartz, opal, chalcedony, &c. at Kosemutcz, in Lower Silesia.

Chrysopras is principally used for ring-stones, and some varieties are highly esteemed; but it is difficult to cut and polish.

Twenty-ninth Species. Flinty Slate.

This has been divided into two sub species, common flinty slate, and Lydian stone.

First Sub-species. Common Flinty Slate. The principal colour is grey, but there are many rarieties of shades. It occurs massive in whole Leds, and frequently in blunt-angled pieces, with a

smooth and glimmering surface. Internally, it is edges; hard, brittle, difficultly frangible, and not parfaintly glimmering; more or less translucent on the tic larly heavy.

It occurs in beds in transitive mountains in Sax

ony, at the lead-hills in Scotland, and other places.

Second Sub-species. Lydian Stone.

The colour is greyish-black, passing into velvetblack. It occurs massive, and is frequently found in trapezoidal-shaped rolled pieces. Internally it is glimmering; opake, hard, pretty easily frangible, and not particularly heavy. It is found in similar formations with the preceding, near Prague and Carlsbad in Bohemia, in Saxony, and in the Moorfoot and Pentland hills near Edinburgh.

When polished, it is used as a test-stone for determining the purity of gold and silver; but is less suited for this purpose than basalt, and some kind of clay slate.

Thirtieth Species. Cat's Eye.

The principal colour is grey, of which it presents many varieties. It occurs in blunt-edged pieces, in rolled pieces, and likewise massive. Internally it is shining; usually translucent, and sometimes also semitransparent. It is hard, easily frangible, and not particularly heavy.

Its geognostic situation is unknown. It is imported from Ceylon and the coast of Malabar; and is usually cut for ring-stones. Some of the varieties are highly valued.

Thirty-first Species. Prehnite.

The colours are various shades of green, white, and yellow. It is sometimes massive, and sometimes crystallized in oblique four-sided tables. Externally, the crystals are smooth and shining; internally, inclining to glistening and pearly.

Prehnite is translucent, sometimes passing into semi-transparent and transparent; it is hard, easily frangible, and not very heavy. It occurs in Dauphiny in veins of the oldest formation; in Scotland in rocks belonging to the newest floetz trap formation ; and was first discovered in Africa by colonel Prehn, from whom it receives its appellation.

Thirty-second Species. Zeolite.

This species is divided by Werner into five subspecies, 1. Mealy zeolite. 2. Fibrous zeolite. 3. Radiated zeolite. 4. Foliated zeolite. 5. Cubic zeolite. As they are principally distinguished from each other by fracture, hardness, and lustre, we shall only observe, that the chief colours of all are yellowish, whitish, and reddish, with a variety of intermediate shades; that zeolite occurs massive, in angular pieces, in balls, and sometimes crystallized in short and oblique four-sided prisms, and in perfect smoothplaned cubes; that it is according to the sub-species opake, translucent, or even transparent; and that it is semi-hard, easily frangible, and not particularly heavy.

Zeolite occurs in rocks belonging to the newest formation, but is sometimes, though rarely, found in primitive green stone, either disseminated, in cotemporaneous balls, or lining or filling up air cavities or veins. All the different sub-species are natives of Scotland. The mealy zeolite is found in the Isle of Sky; the fibrous and radiated in the isles of Canary and Sky; the foliated in Staffa, and the cubic in the same isle, and likewise in Sky. They are likewise met with in Iceland, in Sweden, in Germany, and the East Indies.

2. Potter's clay is of two kinds, earthy and slaty. The earthy is of a yellowish and greyish-white colour in general; occurs massive; is opaque, colours a little, feels somewhat greasy, and adheres strongly to the tongue. Slaty potter's clay is generally of a dark ash-grey colour, and feels more greasy than the precerling. It occurs in great rock masses, and in alluvial land. Both kinds are universally distributed, and are of great importance in the arts and in domestic economy.

5. Pipe clay is greyish-white, passing into yellowish-white, occurring massive, of a glimmering lustre, and having its particles pretty coherent. It feels rather greasy, is easily frangible, and adheres pretty strongly to the tongue.

4. Variegated clay is commonly white, red, and yellow, striped, veined, and spotted. It occurs massive, is soft, passing into friable, feels a little greasy, and adheres somewhat to the tongue. It is found in Upper Lusatia.

5. Clay-stone is commonly grey or red, with various intermediate tints. It occurs massive, is dull, opaque, soft, pretty easily frangible, feels rather meagre, and does not adhere to the tongue. It forms vast rock masses, occurs in beds and veins, and is found in Saxony, in Scotland, and in Shetland.

6. Slate clay is of a grey colour, presenting several varieties. It is massive, internally dull, opaque, pretty soft, mild, easily frangible, adheres a little to the tongue, and feels meagre. It is generally found wherever the oval, floetz trap, and alluvial formations occur.

Eleventh species. Polier, or polishing-stone, Is of a yellowish-grey colour, striped, and the colours alternate in layers. It occurs massive, is dull, very soft, adheres to the tongue, feels fine but meagre, and is nearly swimming. It is found in the vicinity of pseudo-volcanoes, though hitherto it has only been discovered in Bohemia.

Twelfth species. Tripoli

Is of a yellowish-grey colour, passing into ashgrey; occurs massive, is internally dull, very soft, feels meagre and rough, does not adhere to the tongue, and is rather light. It is found in veins and beds in floetz rocks in Saxony, in Derbyshire, and many other countries besides Tripoli, from whence it was first brought. Its use in polishing

metals and minerals is well known.

Thirteenth species. Alum-stone

Is of a greyish-white colour, occurs massive, shews a tendency to crystallization, is soft, passing to friable, and light. It is found at Tolfa, near Rome, from whence the famous Roman alum is manufactured.

Fourteenth species. Alum-earth. The colour is a blackish-brown, and brownishblack; it is massive, dull, feels a little meagre, and somewhat greasy; is intermediate between soft and friable, and light. It is found in beds of great magnitude in alluvial land, and in floetz trap formation in several parts of Germany, in Naples, and in France. It is lixiviated to obtain the alum it contains.

Fifteenth species. Alum-slate

Is divided into two sub-species, as follow: 1. Common alum-slate is between a greyish and Blueish-black colour, occurs massive, and in balls, VOL. VIII.

is soft, not very brittle, easily frangible, and not very heavy.

2. Glossy alum-slate is of an intermediate colour, between blueish and iron-black; occurs massive, with a shining semi-metallic lustre, and in other respects resembles the former. It is found in beds and strata in Saxony, France, Scotland, and Hungary; and affords considerable quantities of alum.

Sixteenth species. Bituminous shule

Is of a brownish-black colour, and occurs massive. Internally, its lustre is glimmering; it is very soft, rather mild, feels rather greasy, is easily frangible, and not particularly heavy.

It is found with clay slate in the coal formation, in Bohemia, England, Scotland, and other coal countries.

Seventeenth species. Drawing slate, or black

chalk.

Its colour is a greyish-black, with a tinge of blue; it occurs massive, is opaque, colours and writes,. is soft, mild, easily frangible, feels meagre but fine, and is rather light.

It is found in primitive mountains in France, Germany, Iceland, Scotland, and the Hebrides. When of a middling degree of hardness, it is used for drawing.

Eighteenth species. Whet-slate.

The common colour is greenish-grey; it is massive; internally, weakly glimmering, semi-hard, feels rather greasy, and is not particularly brittle or heavy. It occurs in primitive mountains in Saxony, Bohemia, and the Levant. When cut and polished, it is used for sharpening knives and tools.

Nineteenth species. Clay-slate.

Its principal colour is grey, of which there are many varieties. It occurs massive; internally its colour is glistening, the substance opaque, seft, pretty easily frangible. It is found in vast strata in primitive and transition mountains in many different countries, but particularly in Scotland. When split into thin and firm tables, it is used for roofing houses, and other purposes.

Twentieth species. Lepidolite.

Its colour is a kind of peach-blossom, red, verging on lilac-blue, and occurs massive. Its internal lustre is glistening; it is translucent, soft, easily frangible, and easily melts before the blowpipe. it lies in gneiss. Hitherto it has only been found in Moravia, where

Its common colour is grey, of great variety of shades. It occurs massive, disseminated in thin tables and layers in other stones, and crystallized either in equilateral six-sided tables, or in six-sided prisms. The surface of the crystals is splendent; internally, shining and splendent. In thin plates, it is transparent; but in larger masses only translucent on the edges. It is semi-hard, feels smooth but not greasy, elastically flexible, and more or less easily frangible.

It forms one of the constituent parts of granite, gneiss, and mica slate, and is almost peculiar to the primitive mountains. It was formerly used iņstead of glass, for windows and lanterns.

Twenty-second species. Pot-stone.

Its colour is a greenish-grey, of different degrees

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of intensity; is massive; lustre, internally, glistening and pearly, translucent on the edges; soft, feels greasy, and is very difficultly frangible.

It occurs in beds, or is indular; and is found in the country of the Grisons, in Saxony, and probably in Hudson's bay, and is nearly allied to indurated tale.

Twenty-third species. Chlorite,

Which see.

Twenty-fourth species. Hornblende, Which see.

Twenty-fifth species. Basalt.

The usual colour is greyish-black, of various degrees of intensity. It occurs massive in blunt and rolled pieces, and sometimes vesicular. Internally, it is commonly dull. It is usually found in distinct concretions, which are generally columnar, and sometimes upwards of 100 feet in length. Commonly opaque, semi-hard, brittle, very difficultly frangible, melts without addition, and is almost exclusively confined to the floetz trap formation. It occurs in strata, beds, and veins, in almost every quarter of the globe, and is very abundant in Scotlaud, Ireland, and in other parts of the British European dominions. It is useful for building, as a touch-stone, as a flux, and in glass manufac

tures.

Twenty-sixth species. Wacke.

The colour is a greenish-grey, of various degrees of intensity. It occurs massive and vesicular, is dull, somewhat glimmering, opaque, usually soft, more or less casily frangible, and not particularly heavy.

It is said to belong exclusively to the floetz trap formation, where it occurs in beds and above clay, and also in veins. It is found in Saxony, Bohemia, and Sweden.

Twenty-seventh species. Clink-stone

Is commonly of a dark greenish-grey colour, always massive, and occurring in irregular columns, and tabular distinct concretions. It is usually translucent on the edges, brittle, easily frangible, and when struck with a hammer sounds like a piece of metal.

It is said to belong to the floetz trap formation, and generally rests on basalt. It is found in Lusatia, Bohemia, South America, and in the isle of Lambash, in the frith of Clyde.

Twenty-eighth species. Lava

Is divided into two sub-species:

1. Slag lava is of a greyish-black colour, passing into other shades. Externally it is spotted, occurs vesicular and knotty, is generally opaque, semihard, brittle, easily frangible, and not particularly heavy.

2. Foam lava is of a dark greenish-grey colour, occurs small and fine, vesicular; externally, glimmering, slightly translucent on the edges, brittle, easily frangible, and light. It has often been confounded with pumice-stone, from which, however, it differs very much. On account of its lightness, it is used with advantage in arching vaults and other kinds of building.

Twenty-ninth species. Green Earth.

Its colour is a celaden green, of various degrees of intensity. It occurs massive, in angular and globular pieces, and also disseminated. Internally, it is dull, streak glistening, very soft, casily frangible, and light.

It is principally found in amygdaloid, in Saxony, Bohemia, Scotland, and other places, and is used by painters.

Thirtieth species. Lithomarge

Is divided into two sub-species.

1. Friable lithomarge, or rockmarrow, is snowwhite, or yellowish-white, occurs massive, as a crust, and disseminated; is generally coherent, feels greasy, and adheres to the tongue. Is found in tin veins, in Saxony.

2. Indurated lithomarge is most commonly white, of which it presents several varieties; is massive; internally dull; streak shining, very soft, easily frangible, feels greasy, and adheres strongly to the tongue. It occurs in veins of porphyry, &c. in Saxony, Bohemia, Bavaria, &c.

Thirty-first species. Rock Soap

and disseminated, dull, opaque, does not soil, writes Is of a brownish or pitch-black colour, massive like drawing-slate, is easily frangible, and adheres strongly to the tongue.

It is found imbedded in rocks of the floetz trap formation, in Poland, and in the isle of Sky, but is very rare, and found only in small quantities.

Thirty-second species. Yellow Earth.

The colour is ochre-yellow, of different degrees of intensity; it is massive, streak somewhat shining, soils, writes, is very soft, adheres pretty strongly to the tongue, and feels somewhat greasy. It occurs in beds with iron-stone, in Upper Saxony, and is employed as a pigment.

To the clay genus, likewise, belong adhesive slate, float-stone, pinite, and umber, which may be considered as recent discoveries.

FIFTH GENUS.

TALC Genus.

First Species. Bole.

Its colour is cream-yellow, passing into various other shades; is commonly massive, very soft, easily frangible, feels greasy, gives a shining streak, adheres to the tongue, and is light. It occurs in rocks belonging to the newest floetz trap formation, and is found in beds of wacke or basalt, in Silesia, Italy, &c. It was formerly employed in medicine, but is now used only as a pigment.

Second species. Native Talc Earth.

The colour is yellowish-grey, passing into creamyellow. It occurs massive, tuberose, and of other shapes; is internally dull, almost opaque, soft, frangible without much difficulty, and adheres a little to the tongue.

It is found in beds of serpentine, but only hitherto in Moravia.

Third species. Meerschaum.

The usual colour is yellowish-white. It occurs massive, is internally dull, opaque, streak shining, is soft, adheres strongly to the tongue, feels a little greasy, and is nearly swimming. It is principally found in Natolia, in Samos, Hungary, Moravia, Spain, and America. It is much used in the manufacture of heads of tobacco-pipes. It is said that the Turks eat it as a medicine.

Fourth species. Fuller's Earth.

The colours are greenish-white, grey, olive, and oil-green. It is massive; internally dull, usually opaque, gives a shining streak, is very soft, feels greasy, and is not particularly heavy.

Ninth species. Tulc.

This is divided into three sub-species.

1. Earthy tale is of an intermediate colour between greenish-white and light greenish-grey; friable, strongly glimmering, soils a little, feels rather greasy, and occurs in tin veins near Freyberg in Saxony.

2. Common or Venetian talc is principally of an apple-green colour, massive and disseminated, and in delicate and small tabular crystals. It is almost always splendent and shining, translucent, in this leaves transparent, flexible, but not elastic; soft, easily frangible, feels very greasy, and approaches to light.

It is almost wholly confined to the primitive mountains, where it is found imbedded in serpentine, and also in veins. It is found in the Tyrolese Alps, in Switzerland, and in Saxony.

3. Indurated tale is of a greenish-grey colour, of various degrees of intensity, occurs massive, is shining, passing to glistening, strongly translucent on the edges, soft, feels rather greasy, and is trangible without particular difficulty. It is found in primitive mountains in Tyrol, Austria, Scotland,

and the Shetland isles.

It is found in beds in primitive mountains, in Saxony, Switzerland, Norway, and Scotland.

3. Glassy actynolite is principally of a mountain-green colour, of various degrees of intensity; occurs massive, or in thin six-sided acicular crystals, is shining and vitreous, strongly translucent, brittle, easily frangible, semi-hard, and is found in similar situations with the preceding.

Thirteenth species. Tremolite.

This is divided into the following sub-species: 1. Asbestous tremolite is of a whitish colour

with a tinge of yellow, grey, red, or green: it occurs massive, and in capillary and acicular crystals; internally glistening, very soft, easily frangible, and

translucent on the edges.

2. Common tremolite is nearly of the same colour as the preceding, occurs massive, and in long and very oblique four-sided prisms: internally, shining and glistening, translucent and semi-transparent, semi-hard, and pretty easily frangible.

3. Glassy tremolite is yellowish, reddish, greyish, and greenish-white; occurs massive, and crystallized. Internally, is shining and pearly; is composed of very thin prismatic concretions, which are again collected into very thick prismatic concretions. It is translucent, brittle, and pretty easily frangible, and is said to emit a phosphoric light when rubbed in the dark.

Tremolite is principally found imbedded in primitive mountains, particularly the mountains of Tremola, in Switzerland. It is also found in different parts of Germany, and in Scotland. Sahlite, lately discovered in Sweden, likewise belongs to the tale genus.

SIXTH GENUS.

CALC Genus.

First species. Rock Milk.

dully, dusty particles generally weakly cohering, Its colour is yellowish white; it is composed of feels meagre yet fine, soils very much, and is very light. It is found in fissures and holes of moun tains composed of floetz lime-stone, in Switzerland.

Second species. Chalk.

Its colour is principally all yellowish-white: it occurs massive, disseminated, and as crust over flint. Internally, is dull, opaque, soils, writes, soft, sometimes very soft, very easily frangible, feels meagre, and rather rough; effervesces strongly with acids, and is found principally on the sea-coast, though the Chiltern range in England is wholly composed of it. It is used for polishing and cleansing metals, glass, &c. and in some places as a manure, and cement in building.

Third species. Lime-stone

Is divided into several sub-species:

1. Compact lime-stone is of two varieties, common compact lime-stone, and roe-stone. The former is generally of a grey colour, but is frequently veined, zoned, striped, or clouded; occurs massive, and in rolled pieces; is translucent on the edges, semi-hard, brittle, pretty easily frangible; is almost entirely confined, like lime in géneral, to the floetz mountains; occurs in sand, stone, and coal formations, in England, Scotland, and many other countries; and is frequently used for building or making roads, or when burnt, for manure and cement.

The latter, or roe-stone, is of a chesnut-brown
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