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Name of Mineral	Common Name	Composition	Hardness	Lustre	Color	Streak
Amphibole. (ăm´fĭ-bōl)	…	Silicate of magnesium, calcium, aluminum, iron, etc.	5–6	Glassy to dull.	Black or light to dark green.	White
Arsenopyrite. (är´sĕn-ō-py̆r´īt)	Mispickel.	Sulphide and arsenide of iron.	6	Metallic.	Silver, yellowish, or light grayish white.	Black.
Barite. (bā´rīt)	Barytes. Heavy spur.	Sulphate of barium.	3	Glassy to stony.	White, yellow, blue or brown.	White.
Biotite. (bī´ō-tīt)	Black Mica.	Hydrous silicate of aluminum, potassium, magnesium and iron.	21⁄2−3	Glassy to almost metallic.	Black or dark brown.	White.
Calcite. (kăl´sīt)	Lime. Calespar.	Carbonate of Calcium.	3	Glassy to earthy.	Colorless or white when pure, all colors when impure.	White.
Chalcocite. (kăl´kŏ-sīt)	Copper Glance.	Sulphide of copper.	3	Metallic; dull when impure or tarnished.	Dark gray. Tarnishes black or green.	Lead-gray.
Chalcopyrite. (kăl´kō-pĭr´īt)	Copper Pyrites. Fools gold.	Sulphide of copper and iron.	4	Metallic.	Bright brass-yellow. Often tarnished iridescent.	Greenish black.
Copper.	…	Native metallic copper.	21⁄2−3	Metallic.	Copper-red. Tarnishes green to black.	Copper-red.
Corundum. (kō-rŭn´dŭm)	…	Oxide of aluminum.	9	Glassy.	All colors; usually gray or brown when massive.	White.
Epidote. (ēp´ĭ-dōt)	…	Basic silicate of calcium, aluminum and iron.	6–7	Glassy to dull.	Dark green or greenish brown (crystals) to light yellowish green.	White.
Fluorite. (flōō´or-īt)	Fluor Spar. Fluorine.	Calcium fluoride.	4	Glassy.	All colors; green, violet, purple, colorless and white, the commoner.	White.
Galenite. (gȧ-lē´nīt)	Galena. Lead.	Sulphide of lead.	3	Metallic.	Bluish lead, gray. Tarnishes black.	Lead-gray.
Garnet.	…	Silicate of various elements: calcium, aluminum and iron are commonest.	61⁄2−71⁄2	Glassy to resinous.	Commonly some shade of red; also brown, yellow, white, black, green.	White.
Gold.	…	Native metallic gold with a little silver, copper, etc.	21⁄2−3	Metallic.	Golden yellow to nearly silver-white.	Yellow to nearly white.
Graphite. (graph´īt)	Black Lead. Plumbago.	Carbon.	1–2	Metallic to dull.	Dark gray to black.	Dark gray.
Gypsum. (jĭp´sŭm)	…	Hydrous sulphate of calcium.	11⁄2−2	Pearly, silky, vitreous, dull.	White, gray, red, yellow or other tints due to impurities.	White.
Halite. (hā´līt)	Rock salt.	Chloride of sodium.	21⁄2	Glassy.	Colorless or white when pure. Yellow, brown, red, etc., when impure.	White.
Hematite. (hēm´ȧ-tīt)	Red oxide of iron.	Oxide of iron.	51⁄2−61⁄2	Metallic to earthy.	Black when metallic; reddish black when dull, red when earthy.	Red.
Limonite. (lī´mŏn-īt)	Yellow oxide of iron.	Hydrous oxide of iron	5–51⁄2	Dull, silky, varnish-like.	Yellow, brown or nearly black.	Yellow or yellowish brown.
Magnetite. (mag´net-īt)	Magnetic iron ore.	Oxide of iron.	51⁄2−61⁄2	Metallic to dull.	Iron-black.	Black.
Malachite. (măl´ȧ-kīt)	…	Hydrous carbonate of copper.	31⁄2−4	Silky to dull.	Green, often nearly black on exposed surfaces.	Green. Paler than the color.
Muscovite. (mŭs´ko̱vīt)	Mica, isinglass. White Mica.	Hydrous silicate of potassium and aluminum.	2–21⁄2	Glassy. Pearly on cleavage faces.	White or light tints of other colors, particularly gray, brown or green.	White.
Orthoclase. (ôr´tho̱-klās)	Feldspar. Potash.	Silicate of potassium and aluminum.	6	Glassy to stony.	Flesh-red, gray, yellow, white or colorless.	White.
Pyrite. (pĭr´īt)	Pyrites. White iron. Fools gold.	Sulphide of iron.	6–61⁄2	Metallic.	Pale to deep brass-yellow. Tarnishes brown or iridescent.	Black.
Pyrolusite. (pĭr´o̱-lū´sīt)	…	Oxide of manganese.	1–21⁄2	Metallic to dull.	Black to dark steel-gray.	Sooty black.
Pyroxene. (pĭr´ŏks-ēn)	…	Silicate of magnesium, calcium, aluminum and iron.	5–6	Glassy to dull.	Black or light to dark green.	White to greenish.
Quartz. (Pheno- crystalline).	…	Oxide of silicon.	7	Glassy.	White or colorless when pure. All colors when impure.	White or light tints.
Quartz. (Crypto- crystalline).	…	…	…	Dull to earthy.	…	…
Serpentine. (sēr´pēn-tīn)	…	Hydrous silicate of magnesium and iron.	4+	Wax-like, silky, earthy.	Light to dark green, yellow, brownish red, variegated.	White.
Siderite. (sĭd´ẽr-īt)	…	Carbonate of iron.	31⁄2−4	Glassy to earthy.	Light to dark brown or gray. Tarnishes reddish brown or brownish black.	White to yellowish.
Sphalerite. (sfāl´ẽr-īt)	Blende, Jack Rosin zinc, zinc, etc.	Sulphide of zinc.	31⁄2−4	Resinous to nearly metallic.	Commonly yellow, brown, black or red; sometimes green or white.	White, yellow or brown.
Stibnite. (stĭb´nīt)	…	Sulphide of antimony.	2	Metallic.	Light gray. Cleavage faces appear silver white when reflecting light.	Lead-gray.
Talc. (tălk)	Talcum.	Hydrous silicate of magnesium.	1–11⁄2	Waxy to dull. Pearly on cleavage faces.	White, light green, gray; other colors when impure.	White to greenish.
Tetrahedrite. (tet´ra-he´drīt)	Gray copper.	Sulph-antimonite of copper.	3–41⁄2	Metallic.	Gray.	Gray, brown, or reddish.
Tourmaline. (tōōr´mȧ-lĭn)	Schorl.	Silicate of boron and various other bases varying with the variety.	7–71⁄2	Glassy to resinous.	All colors. Interior and exterior or opposite ends of a crystal may differ in color.	White.
Zoisite. (zois´īt)	…	Silica, alumina, lime, peroxide of iron, water.	6	Pearly.	White, gray, yellow, brown.	Uncolored.

Name of Mineral	Cleavage or Fracture	Crystallization and Occurrence	Tenacity etc.	Diaphaneity	Varieties	Remarks
Amphibole. (ăm´fĭ-bōl)	Perfect in two directions at angle of 124°.	Prismatic crystals with hexagonal cross-section, common; also cleavable masses.	Brittle to tough.	Opaque to transparent.	Actinolite (green, transparent). Asbestos (fibrous, dull). Hornblende (black).	Common constituent of igneous and metamorphic rocks. Valueless.
Arsenopyrite. (är´sĕn-ō-py̆r´īt)	Good in two directions at an angle of 112°. Not evident on fine grained material.	Crystals resemble a double-edged axe. Occurs also coarse to fine granular.	Brittle.	Opaque.	…	Principal ore of arsenic and sometimes carries gold. Gives sparks and garlic odor when struck with a hammer. Yellow tarnish.
Barite. (bā´rīt)	Perfect in one direction; two other good cleavages at right angles to the first and at 101° with each other.	Diamond shaped or rectangular tabular, or prismatic crystals and platy masses.	Brittle.	Transparent to translucent.	…	Used to adulterate white lead and give weight to paper. Often associated with lead ores. Very heavy.
Biotite. (bī´ō-tīt)	Very perfect in one direction, yielding thin sheets.	Six-sided tabular crystals, and as scales, plates, or scaly masses.	Flexible. and elastic.	Opaque to transparent.	…	Common constituent of igneous rocks. May be brittle when altered. Valueless.
Calcite. (kăl´sīt)	Perfect in three directions at angles of about 105° or 75°.	Prismatic or tabular six-sided crystals; also granular, cleavable, or earthy masses.	Brittle.	Transparent to opaque.	Marble (granular). Limestone (dull, compact). Chalk (soft, white, earthy). Mexican Onyx (compact, banded).	Effervesces vigorously in hydrochloric acid of any strength and temperature. Used as flux, building or ornamental stone, to make lime, etc.
Chalcocite. (kăl´kŏ-sīt)	No cleavage, smooth conchoidal fracture.	Usually very compact masses; six-sided, tabular crystals rare.	Slightly sectile.	Opaque.	…	An important ore of copper. Cuts easily, yielding a highly polished surface.
Chalcopyrite. (kăl´kō-pĭr´īt)	No cleavage. Uneven fracture.	Occurs massive or in scattered particles. Crystals usually have four triangular faces.	Brittle.	Opaque.	…	One of the most important ores of copper and often carries silver and gold. Is often mistaken for the latter.
Copper.	No cleavage. Hackly fracture.	Masses, plates, scales, branching aggregates and octahedral crystals, usually distorted.	Malleable sectile.	Opaque.	…	The value and uses of copper are well known. Often carries some silver.
Corundum. (kō-rŭn´dŭm)	Often parts readily into almost rectangular pieces whose faces are cross-hatched.	Prismatic or tabular six-sided crystals; also granular and pseudo-cleavable masses.	Brittle to tough.	Translucent to transparent.	Ruby (red). Sapphire (blue, etc.). Adamantine. Spar (massive). Emery (granular, impure).	A very valuable gem mineral and a fine abrasive. See plate I, figures 10, 11 and 13.
Epidote. (ēp´ĭ-dōt)	Perfect in one direction.	Slender, deeply grooved prismatic crystals and cleavable to fine granular masses.	Brittle.	Transparent to opaque.	…	Common constituent of metamorphic rocks. Rarely cut as a gem.
Fluorite. (flōō´or-īt)	Cleaves easily into octahedrons, i.e., in four directions, at angles of 109° or 71°.	In groups of crystals, usually cubical; also in cleavable masses. Sometimes granular.	Brittle.	Transparent to translucent.	Rock fluorite (finely granular and usually very impure and hard).	Used as a flux in smelting ores, and in several arts and trades.
Galenite. (gȧ-lē´nīt)	Perfect cubical, i.e., in three directions at angle of 90°.	Cubical crystals, often with triangular faces on the corners; also, cleavable to granular masses.	Very Brittle.	Opaque.	Steel with galena (very fine grained masses). Often rich in silver.	Most important lead and silver ore. Often contains the latter metal with sometimes gold and other elements.
Garnet.	No cleavage. Uneven fracture.	Complex, rounded crystals, glassy masses and granular.	Brittle.	Transparent to opaque.	…	An important abrasive and a beautiful gem. Found in metamorphic rocks. See plate I, figures 8 and 15.
Gold.	No cleavage. Hackly fracture.	Nuggets, plates, scales, wires; branching aggregates and distorted crystals, usually octahedral.	Malleable sectile.	Opaque.	Based upon and named after any impurities that may be present.	The value and uses of gold are well known.
Graphite. (graph´īt)	Perfect in one direction. Cleavage faces are apt to be curved. Not shown if finely granular.	Imbedded scales and foliated, granular or compact masses. Rarely in six-sided, tabular crystals.	Sectile Flexible.	Opaque.	…	Used in the manufacture of lubricants, infusible crucibles, and “lead” pencils.
Gypsum. (jĭp´sŭm)	Very perfect in one direction; two others show as cracks at angle of 114°, on the perfect cleavage faces.	Diamond shaped crystals, and cleavable, fibrous, granular, foliated or compact masses.	Sectile, Thin flakes, flexible.	Translucent to transparent.	Selenite (cleavable, transparent). Satin spar (white, fibrous, silky). Alabaster, (white, fine grained).	Is carved into vases, statues, etc., and forms plaster of paris when calcined and ground. Is a precipitate rock.
Halite. (hā´līt)	Perfect cubic i.e., in three directions at angle of 90°.	Cubical or octahedral crystals; also cleavable, granular or compact masses.	Brittle.	Translucent to transparent.	…	Tastes salty. Enormous quantities are used to season food, in various arts and trades, and as a source of sodium and its salts. A precipitate rock.
Hematite. (hēm´ȧ-tīt)	No cleavage; may have a parting in one direction producing a platy structure. Uneven fracture.	Complex, tabular or rounded crystals; also platy, oolitic, earthy, micaceous, and kidney shaped masses.	Brittle.	Opaque.	Specular iron (mirror-like plates or crystals). Red Ochre or Ruddle (red, earthy).	The most important ore of iron, and is also used to make cheap paint, polishing powder, etc.
Limonite. (lī´mŏn-īt)	No cleavage. Uneven fracture.	Botryoidal or stalactitic forms with a radiating fibrous structure and a varnish-like surface, also earthy masses and concretions.	Brittle.	Opaque.	Bog iron ore (porous, earthy, often encloses vegetation). Yellow ochre or umber (earthy with clay, etc.)	Commonest, but most impure ore of iron, and is also used to make cheap yellow and brown paint.
Magnetite. (mag´net-īt)	No cleavage. Sometimes parts in four directions at angles of 109° and 71°. Uneven to subconchoidal fracture.	Octahedral crystals, and coarse to fine granular, laminated, or compact masses.	Brittle.	Opaque.	Lodestone (a natural magnet).	The only black, brittle, magnetic mineral, and a very pure and valuable ore of iron.
Malachite. (măl´ȧ-kīt)	No cleavage. Uneven fracture.	Massive, as botryoidal crusts with a radiating structure and silky lustre, and as slender crystals forming velvety surfaces.	Brittle.	Translucent to opaque.	…	Is an ore of copper and is used as an ornamental stone and in jewelry. Azur-malachite is malachite mixed with blue azurite. See plate I, figure 4.
Muscovite. (mŭs´ko̱vīt)	Very perfect in one direction, yielding thin sheets.	Six-sided, tabular crystals, and as scales, plates, or scaly masses.	Flexible and elastic.	Transparent to translucent.	…	Used in stove doors, as insulation in electrical apparatus, and for spangling or frosting paper and fabric.
Orthoclase. (ôr´tho̱-klās)	In two directions at angle of 90°, one direction slightly less perfect than the other.	Thick-set square or six-sided crystals, or cleavable masses or grains.	Brittle.	Transparent to opaque.	Sanadine (transparent crystals or grains imbedded in igneous rocks).	Associated with quartz and mica in many rocks. Used in making glass and porcelain. Next to quartz in frequency of occurrence.
Pyrite. (pĭr´īt)	No cleavage. Conchoidal to uneven fracture.	Cubical, octahedral, or complexly rounded crystals, coarse to fine granular, and massive.	Brittle.	Opaque.	…	Used in making sulphuric acid and often contains so much gold, silver and copper as to make it an ore of these metals.
Pyrolusite. (pĭr´o̱-lū´sīt)	May appear to have good cleavage in one direction but usually shows none.	Occurs as radiating prismatic layers, velvety crust and granular to compact masses. Soils the fingers.	Brittle.	Opaque.	…	Has many uses and is valuable. Usually associated with a very fine grained, hard, black mineral that is often botryoidal.
Pyroxene. (pĭr´ŏks-ēn)	Poor in two directions at angle of nearly 90°. May have a fine platy parting.	Prismatic crystals with square or octagonal cross-section; also foliated and massive.	Brittle.	Transparent to opaque.	Diopside (light green, glassy). Diallage (light green, dull, foliated). Auagite (black).	A common constituent of igneous rocks. Diopside is sometimes used as a gem.
Quartz. (Pheno- crystalline).	No cleavage. Single crystal has conchoidal fracture, otherwise the fracture is uneven.	Six-sided prism terminated by a six-sided pyramid; also massive, coarse to fine granular, and as sand.	Brittle.	Transparent.	Rock crystal (colorless, transparent). Amethyst (purple). Rose (pink). False topaz or Citrine (yellow). Smoky quartz or Topaz (brown or gray). Milky (white). Ferruginous (iron stained).	The commonest of all minerals. A constituent of most rock. Great quantities are used as a flux in smelting, as abrasives, and in the manufacture of glass and porcelain. The transparent varieties of pleasing tints are used as gems. Water-clear spheres are very valuable.
Quartz. (Crypto- crystalline).	No cleavage. Conchoidal fracture.	Very fine grained massive, botryoidal, nodular, or filling or lining cavities in rocks.	Brittle.	Translucent to opaque.	Chalcedony (drab). Carnelian (red, translucent). Jasper (red, brown, yellow, opaque). Heliotrope or Bloodstone (dark green with red spots). Flint (dark gray concretions). Agate (banded or particolored). Onyx (agate with flat layers). Petrified wood (wood replaced by quartz).	…
Serpentine. (sēr´pēn-tīn)	No cleavage. Conchoidal fracture when massive.	Compact, massive or coarse to fine fibrous. The two habits are often in parallel layers.	Tough. Fibres are flexible.	Translucent to opaque.	Precious or noble (massive, translucent). Chrysolite (silky, fibres). Verde antique (massive with calcite).	Chrysolite is the best commercial asbestos. Other varieties are used as ornamental stone and occasionally in jewelry.
Siderite. (sĭd´ẽr-īt)	Very perfect in three directions at angle of 107° and 73°. Not evident when fine grained.	Cleavable masses, coarse to fine, granular and at warped crystals that resemble distorted cubes.	Brittle.	Translucent to opaque.	Sphaerosidirite or Clay-ironstone (concretions of fine grained siderite mixed with clay).	The most valuable ore of iron, but is rather uncommon. The impure clay-ironstone is fairly common in sediments.
Sphalerite. (sfāl´ẽr-īt)	Very perfect in six directions at angles of 60°, 90° and 120°.	Complexly rounded or modified cubical crystals; also cleavable, coarse to fine granular masses, and botryoidal, etc.	Brittle.	Transparent to opaque.	…	The commonest zinc ore and an impure variety furnishes most of the cadmium of commerce. Associated with galenite and silver minerals.
Stibnite. (stĭb´nīt)	Perfect in one direction, yielding blade-like strips which are bent or hatched perpendicular to their length.	Sharp, vertically grooved, prismatic crystals and in cleavable masses with a bladed structure.	Very brittle.	Opaque.	…	The chief source of antimony and its salts. Sometimes carries gold and silver.
Talc. (tălk)	Perfect in one direction, yielding thin flexible plates. Not shown on the fine grained soapstone.	Foliated, coarse to fine granular, or compact masses. Feels greasy to soapy.	Tough sectile.	Transparent to translucent.	Steatite or soapstone (granular, impure, hardness up to 21⁄2). French chalk (white, fine grained soft).	Used in making porcelain, polishing powder, lubricants, gas jets, tinted plasters, paper, soap, leather dressing, talcum powder, slate pencils, and in other ways.
Tetrahedrite. (tet´ra-he´drīt)	No cleavage. Uneven, granular fracture.	Crystals have four triangular faces. Occurs usually granular massives.	Brittle.	Opaque.	…	Often contains enough silver to make it a valuable ore of this metal as well as copper.
Tourmaline. (tōōr´mȧ-lĭn)	No cleavage. Uneven to poor conchoidal fracture.	Vertically lined, prismatic crystals with spherical triangular cross-sections. Also columnar or compact massive.	Very brittle.	Transparent to opaque.	Schorl (black). Rubellite (pink). Indicolite (blue). Achroite (white).	A popular semi-precious gem. When heated (not above 212° F.), will usually pick up bits of paper. Opposite ends of crystals have different forms.
Zoisite. (zois´īt)	Parallel cleavage; sometimes fibrous.	Occurs in tri-metric crystals; also massive.	Brittle.	Transparent, translucent.	…	Often a constituent of metamorphic rocks.

Antimony and Bismuth. Antimony is produced in Germany, France, Italy, Hungary, United States, Japan and other countries.

Bismuth comes mainly from Bolivia and Australia. Some is produced in Saxony and England.

Stibnite (antimony sulphide) is the chief ore of antimony. Bismuth occurs in small amounts in a pure state and also combined with sulphur.

These metals form many alloys such as type metal, anti-friction metals, white metal, babbitt metal, fusible metals.

Tartar emetic and other antimony compounds are used in medicine and dyeing.

Amber is a fossil resin found chiefly along the shores of the Baltic. It is used in making mouthpieces for pipes, cigar holders, beads and other articles.

Arsenic. Germany, England, Canada, the United States and Spain produce the ores. Chemical laboratories transform them into the useful compounds.

Arsenopyrite (arsenic and iron sulphide), orpiment and realgar (sulphides of arsenic) and the sources of arsenic.

Arsenic (white arsenic, arsenious acid or oxide of arsenic), paris green and other compounds and salts are prepared.

Sheep dip, rat poison, insecticides, embalming fluid, pigments and dyes are prepared with arsenic compounds. Arsenic salts are used in preparing certain coal-tar colors.

Asphaltum (or mineral pitch) is a bituminous mineral substance found more or less pure, in some localities. The pitch lake of Trinidad and the Bermudez lake at the mouth of the Orinoco in Venezuela, are the largest known deposits of moderately pure asphalt. Smaller deposits of high grade occur in Utah, Cuba and the Barbadoes.

Rock asphalt consists of sandstone or limestone impregnated with asphalt. Much asphalt is produced in refining certain grades of petroleum—such as those obtained in California and Texas.

Rock asphalts are mined in France, Switzerland, Sicily, California, Kentucky and Oklahoma.

For paving rock asphalts are much used in Europe. Trinidad and Venezuelan asphalts are exported in large quantities to the United States and Europe. For paving, these lake asphalts are mixed with broken stone, sand and petroleum residuum.

Pure varieties (gilsonite, marjak, glance pitch) are made into black varnish, used for insulating, etc.

Barium is mined in the United States and Germany.

Barytes or barite is a heavy, white mineral (barium sulphate). It is used as a substitute or adulterant for white lead in paints, and in making oxygen.

Bismuth. See antimony.

Building Stones are quarried for local use in all parts of the world.

Granite, syenite, gneiss, basalt and other hard or durable rocks.

Only stone of exceptional beauty is shipped to a great distance. Scotland, Norway, Massachusetts, Maine and other localities produce fine stones.

Calcium has no commercial use in the metallic state. Its compounds, both natural and artificial, are of great economic importance.

Limestone (calcium carbonate) is a very common rock used for building. It may be of almost any color and coarse or fine in texture. It is found and utilized in all parts of the world. In the United States, Pennsylvania, Illinois, Ohio, Indiana, New York and Missouri are the chief producers.

Lime is used in chemical industries and mortar.

Marble is a name applied to limestones suitable for polishing or ornamental work. Mexican onyx is translucent. Fine marbles are quarried in Italy, Egypt, France, Spain and Greece. Vermont, Georgia, Tennessee and New York supply the greater part of the marble used in the United States. Handsome marbles are imported from Carrara, Italy, and other parts of Europe. Mexican onyx is also imported.

Chalk comes mainly from the south of England. We export some Portland cement and import a little from Europe.

Chalk is of peculiar soft texture; whiting is prepared chalk used to make putty and paints; precipitated chalk is similar.

Lime is made by burning (calcining) common limestones. Portland and hydraulic cements are prepared by calcining siliceous limestones or a mixture of limestone and clay. They are of enormous commercial importance, being used in concrete construction work. Europe and the United States produce large quantities. Pennsylvania is the leading state in this industry.

Buildings (both commercial and residences) are now being extensively constructed of cement—in the former case being re-enforced by iron rods.

Chloride of lime (or bleaching powder), acetate of lime, calcium carbide and many other compounds are of industrial value.

Gypsum (hydrous calcium sulphate) is used in fertilizers. Plaster is prepared by calcining (burning) gypsum. Plaster of paris is its purest form. Alabaster is compact white gypsum. It is a common mineral mined in many parts of the world. Michigan, Kansas, New York, Ohio and other states produce it. Fertilizers and plaster use up large quantities of this mineral. Plaster of paris is used for casts, decorative plaster work, cement, etc.

Fluorite (calcium fluoride) is a less common mineral. Mined in England, Kentucky and Illinois. It is used in chemical manufacture and as a flux for ores.

Phosphate rock (chiefly calcium phosphate) is important in the preparation of fertilizers, and chemicals containing phosphorus. It is found in deposits of organic origin in South Carolina, Florida, Tennessee, the West Indies, Canada, Spain, France, Germany and England.

The natural phosphates are treated with sulphuric acid as a first step in the manufacture of phosphatic fertilizers. Exported in large amount to Germany, England and other countries.

Carborundum, or carbide of silicon, is harder than any known substance but the diamond. [109] Much is manufactured at Niagara Falls, by electrically heating a mixture of coke, sand and salt. It is used for making polishing powder, in grinding wheels, sharpening stones, abrasive cloth, etc.

Cerium. See rare metals.

Chrome is mined in Asia Minor, Greece, Canada, New Caledonia and California. Its salts are prepared in chemical laboratories.

Chromite (oxide of chromium and iron) is the only ore.

Bichromate of potash is the most important compound. It, together with chromic acid, is used in tanning soft leather. A small percentage added to steel makes it very hard and suitable for burglar-proof safes, tools, etc. Salts of chrome are used for dyes and pigments, such as chrome yellow, chrome green, etc.

Coal is one of the most important of all rocks and first among fuels. It consists chiefly of carbon, and is universally regarded as of vegetable origin.

Several theories as to the origin of coal have been put forth from time to time. The one now generally accepted is that the rank and luxuriant vegetation which prevailed during the carboniferous age grew and decayed upon land but slightly raised above the sea; that by slow subsidence this thick layer of vegetable matter sank below the water, and became gradually covered with sand, mud, and other mineral sediment; that then, by some slight upheaval or gradual silting up of the sea bottom, a land surface was once more formed, and covered with a dense mass of plants, which in course of time decayed, sank, and became overlaid with silt and sand as before. At length, thick masses of stratified matter would accumulate, producing great pressure, and this, acting along with chemical changes, would gradually mineralize the vegetable layers into coal.

In passing from wood or peat to coal, the proportion of carbon increases, while that of oxygen and hydrogen decreases, these substances being given off in the form of marsh-gas and carbonic acid gas in the process of decay.

Deposits occur in almost all parts of the world, but many are almost entirely undeveloped; as, for example, the coal fields of China. The largest production is in the United States, Wales, England, Germany, Austria, Russia and Australia. Mines are worked in India, Japan, Mexico, South America, South Africa, China and the Philippines. Pennsylvania, Ohio, West Virginia, Alabama, Indiana, Iowa and many other states mine coal in great amount. Pennsylvania produces nearly all of the anthracite and a large quantity of bituminous coal.

Bituminous coal, coking coal, non-coking coal, cannel coal, cherry coal, splint coal, gas coal, steam coal, etc., are all varieties of soft coal and contain a considerable percentage of volatile matter.

Bituminous coal is the fuel which runs the factories, railways and steamships of the world. The distillation of coal tar and the utilization of its numerous by-products, is one of the best examples of modern economy which turns waste material into useful products and large profits. Much coke is made without saving the by-products.

By distillation, bituminous coal yields gas, ammonia, coal tar and coke. Coal tar products are numbered by the thousand. Among them are naphtha, benzine, oil of mirbane, perfumes, flavors, drugs, saccharine, aniline and other dyes, phenol, carbolic acid, salicylic acid, naphthaline, photographic developers, creosote, oils, tar and pitch.

Anthracite coal is almost pure carbon.

Cobalt is a metal the ores of which are sparingly distributed. It generally occurs as Speiss-cobalt, cobalt-glance (or cobaltite), wad, cobalt-bloom, linnæite and skutterudite. Its minerals are found chiefly in the Erzgebirge Mountains, Sweden, Norway, Chile, in silver ores near Coleman township, Ontario, in Oregon (as garnierite), and in New Caledonia. The metal itself is of a gray color with a reddish tinge, brittle, hard, and very magnetic.

Many of its compounds are valued on account of the brilliance and permanence of their colors. The protoxide of cobalt, is employed in the form of smalt in the production of the blue colors in porcelain, pottery, glass, encaustic tiles, fresco-painting, etc., and forms the principal ingredient in Old Sevres Blue, Thenard’s Blue, etc. The chlorid of cobalt, dissolved in much water, may be employed as a sympathetic ink. In dilute solutions, it is of a faint pink color, which is not observable upon paper; but when heated before the fire, it loses water, and becomes blue, and the writing is then capable of being read.

Copper is, next to iron, the most important metal in use. Its greatest production is in the United States, in Arizona, Montana, Michigan, and Utah. Spain, Japan, Chili, Australia and Germany produce smaller amounts. The metal is purified by smelting, and refined, often by electrolytic methods. There are many ores.

Chalcopyrite and bornite (sulphides of copper and iron) are widely distributed.

Chalcocite (copper sulphide) is mined in Montana, malachite and azurite (carbonates of copper) in Arizona and metallic copper in Michigan.

Copper matte is the crude metal as it comes from the smelter.

Brass and bronze are alloys of copper with zinc, tin, aluminum, etc.

Copper sulphate (blue vitriol) is the most important chemical compound of copper.

The value of copper has increased within recent years, due to its enormous use in electrical work. Aside from this, copper is employed in large amount in the various alloys into which it enters, and in coins, utensils, printing plates, etc. Copper sulphate is extensively used in electrical apparatus dyes, chemical work and as an antiseptic. Large amounts of manufactured copper are exported to Europe. Smaller quantities of ores, matte and regulus are imported from Mexico, South America and other countries. Copper wire is extensively used by telephone and telegraph companies.

Diamond. See gems.

Gems, or Precious Stones are those which, because of their beauty, hardness, and rarity, are prized for use in ornamentation, especially [110] in jewelry. The diamond, ruby, sapphire, and emerald are the only stones which are, strictly speaking, entitled to be called “precious” in this sense; but the opal, on account of its beauty, is often classed with the precious stones; as is also the pearl, which is really not a stone, but a secretion of a shellfish.

Alexandrite.—A variety of chrysoberyl found in the mica slate of the Ural mountains. It is of a rich garnet color by artificial light, by daylight of a dark moss green. It is the only stone that so changes. The finest specimens of alexandrite are nearly as valuable as diamonds.

Amethyst.—A variety of crystallized quartz of a purple or bluish-violet color, of different shades. It is much used as a jeweler’s stone. The lighter colored ones come from Brazil, the deep purple ones from Siberia. In value they are about the same as the garnet.

Beryl.—A very hard mineral of much beauty when transparent. It occurs in hexagonal prisms, commonly of a green or bluish-green color, but also yellow, pink and white. It is a silicate of aluminum and glucinum. Beryls are very rich in colors.

Bloodstone.—A green siliceous stone sprinkled with red jasper, whence the name.

Cameo.—A figure cut in stone or shell that is composed of different colored layers. The value depends on the artistic merit of the engraved figure.

Carbuncle.—A beautiful gem of a deep red color (with a mixture of scarlet), found in the East Indies. When held up to the sun it loses its deep tinge, and becomes of the color of a burning coal.

Carnelian.—A variety of chalcedony, of a clear, deep red, flesh-red, or reddish-white color. It is moderately hard, capable of a good polish, and often used for seals. It is now used but little.

Cat’s-eye.—A variety of quartz or chalcedony exhibiting opalescent reflections from within, like the eye of a cat. The name is given to other gems affording like effects, especially the chrysoberyl.

Chalcedony.—A translucent variety of quartz, having usually a whitish color, and a luster nearly like wax.

Dendrite.—A stone or mineral in which are branching figures, resembling shrubs or trees, produced by a foreign mineral, usually by an oxide of manganese, and the moss agate.

Diamond.—A precious stone or gem excelling in brilliancy, beauty of prismatic colors, and remarkable for extreme hardness. It is found in many hues—green, rose, straw, yellow, etc.—but the straw-colored ones are the most common. The diamond is a native carbon, occurring in isometric crystals, often octahedrons, with rounded edges. It is the hardest substance known. Diamonds are said to be of the first water when very transparent, and of the second and third water as the transparency decreases.

Diopside.—A crystallized variety of pyroxene (a silicate of lime and magnesia), of a clear, grayish-green color; also called mussite.

Emerald.—A precious stone of a rich green color; it is the most valuable variety of beryl. (See beryl.)

Epidote.—A mineral, commonly of a yellowish-green color, occurring granular, massive, columnar, and in crystals. It is a silicate of alumina, lime, and oxide of iron, or manganese.

Fluorite.—Calcium fluoride, a mineral of many different colors, white, yellow, purple, red, etc., often very beautiful. When crystallized it is commonly in cubes with perfect octahedral cleavage. Some varieties are used for ornamental vessels. Also called fluor spar, or simply fluor. The colored varieties are often called false ruby, false emerald, false topaz, false sapphire, and false amethyst.

Flint.—A massive, somewhat impure variety of quartz, in color usually of a gray to brown or nearly black. (See quartz.)

Garnet.—A mineral having many varieties, differing in color and in their constituents, but with the same general chemical formula. The commonest color is red; the luster is vitreous, or glassy; and the hardness is greater than that of quartz, about half as hard as the diamond. Besides the red varieties there are also white, green, yellow, brown and black ones.

The garnet is a silicate with various bases. The transparent red varieties are used as gems. The garnet was the carbuncle of the ancients. Garnet is a very common mineral in gneiss and mica slate.

The finest specimens of red garnets come from Arizona and a single carat stone is worth about two dollars. A green variety that comes from Russia is worth about half as much as the diamond.

Heliotrope or bloodstone.—A green siliceous stone sprinkled with jasper, as if with blood, whence the name.

Hyacinth.—A red variety of zircon, sometimes used as a gem. It resembles closely a dark Spanish topaz, and is worth a little more than the garnet.

Indicolite.—A variety of tourmaline of an indigo-blue color.

Iolite.—A silicate of alumina, iron, and magnesia, having a bright blue color and a vitreous or glassy luster. It is remarkable for its dichroism, and is also called dichroite.

Jacinth.—Same as hyacinth.

Jade.—A stone commonly of a pale to dark green color, but sometimes whitish. It is hard and very tough, capable of a fine polish, and is used for ornamental purposes and for implements, especially in eastern countries and among many primitive peoples.

Jasper.—An opaque, impure variety of quartz, of red, yellow, and other dull colors, breaking with a smooth surface. (See quartz.)

Labradorite.—A kind of feldspar, commonly showing a beautiful play of bluish-gray colors, and, hence, much used for ornamental purposes. The finest specimens come from Labrador.

Lapis-lazuli or lazuli.—A mineral of a fine azure-blue color, usually occurring in small rounded masses. It is essentially a silicate of alumina, lime, and soda, with some sodium sulphide. It is often marked by yellow spots or veins of sulphide of iron, and is much valued for ornamental work.

Moonstone.—A nearly pellucid variety of feldspar, showing pearly or opaline reflections from within.

The best specimens come from Ceylon. Their value is not much more than the expense of cutting.

Obsidian.—A kind of glass produced by volcanoes. It is usually of a black color and opaque, except in thin splinters.

Onyx.—Chalcedony in parallel layers of different shades of color. It is used for making cameos, the figure being cut in one layer with the next layer as a background (see cameo). It is stained black and used to make mourning jewelry.

Opal.—A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity. The precious opal shows a peculiar play of colors of delicate tints and it is highly esteemed as a gem. One kind, with a varied play of colors in a reddish ground, is called harlequin opal. The fire opal (which comes from Mexico) has colors like the red and yellow of flame. This is not the cheap variety commonly called Mexican opal.

CELEBRATED HISTORIC DIAMONDS OF THE WORLD