Part 5

Iridescent or rainbow quartz is the variety of rock-crystal containing cracks and fissures which reflect all the colors of the rainbow. Quartz can also be artificially colored by rapidly cooling a heated specimen and then dipping the piece into a coloring preparation; the minute cracks in the quartz absorb the coloring matter, and the result is a red-, blue-, or green-tinted stone.

The massive varieties of quartz embrace the rose quartz, avanturine, cat’s-eye, crocidolite, heliotrope, chrysoprase, prase, plasma, chalcedony, agates, onyx, carnelian, jasper, hornstone, and flint.

ROSE QUARTZ.

Rose quartz occurs in a massive form, usually very imperfect and cracked, and varying in color from rose-red to pink. The color is supposed to be due to titanic acid, and often becomes paler on exposure.

This stone is nearly opaque and semi-transparent on the edges, has a greasy lustre, and specific gravity of 2.65 to 2.75. Rabenstein near Zwiesel in Bavaria, the United States, Brazil, France, Ceylon, Finland, and Siberia are places where rose quartz has been found.

AVANTURINE.

Avanturine is an opaque, yellow, brown, or red quartz, spangled with minute scales of mica or some other mineral, and found principally near Madrid, in Spain. It is also found in France, Scotland, Bavaria, the Urals, and Styria.

A beautiful imitation of avanturine, called goldstone, is manufactured of glass into which metal filings are introduced. This goldstone is superior to avanturine in every point except that of hardness. Avanturine and its imitation, but largely the latter, are used for the cheaper kinds of jewelry, and were very popular in the United States some years ago.

CAT’S-EYE.

The Hungarian, occidental, or quartz cat’s-eye is found on the coast of Malabar, Ceylon, Hartz Mountains, and Bavaria.

This stone is translucent to opaque, gray, green, brown, red, and the shadings of these colors, but usually a greenish-gray, with a mass of fine white lines in the centre, which give to the stone a chatoyant appearance.

The cat’s-eye is usually cut cabochon or carbuncle-shaped, and the lines (which are due to the fibres of asbestos) are kept in the centre of the stone, and play like the eye of a cat when the stone is moved.

The quartz cat’s-eye is easily distinguished from the oriental of chrysoberyl cat’s-eye, as it is softer and much lighter.

CROCIDOLITE.

Crocidolite or tiger-eye is a light-brown, brownish-yellow to dark-green, and greenish-blue quartz, which has the same chatoyant qualities as the cat’s-eye. When cut cabochon, the crocidolite is called tiger-eye.

This beautiful mineral was very rare some years ago, and good specimens were sold by the carat.

Great quantities, however, have lately been found in South Africa, and although the finest pieces are still used for cameos and intaglios, many objects, such as paperweights, umbrella handles, match-safes, etc., are now cut from this stone.

Crocidolite is often artificially colored to very closely imitate some of the finest shades of the oriental cat’s-eye.

HELIOTROPE.

Heliotrope or blood-stone, as this variety is commonly called, is a dark-green quartz, translucent to opaque, and covered with small red spots or blood-colored blotches, from which the stone derives the name of blood-stone.

This stone has long been used for seal and signet purposes, and many fine intaglios and cameos carved in blood-stone are in existence.

Bucharia, Tartary, Siberia, East India, China, the island of Rum in the Hebrides, the United States, and Canada are some of the places where the heliotrope is found.

CHRYSOPRASE.

The chrysoprase is an apple-green chalcedony, sometimes olive- or whitish-green. It is translucent, scratches glass, and has the specific gravity of 2.56.

The color is due to the presence of oxide of nickel. This stone is found principally in Silesia, but also in Siberia and the United States.

Large pieces of chrysoprase are rare, and even the best specimens lose their color in course of time.

PRASE.

A translucent, spotted leek-green, green quartz, which loses its polish on exposure to the air, is known as prase.

This stone is found principally in the iron mines of Brietenbaum, Saxony, and also in Brittany, the Tyrol, Scotland, Salzburg, Finland, and the United States.

Prase is sometimes known commercially as “mother of emerald,” and a greenish crystalline quartz is also often called prase.

PLASMA.

Plasma is a dark grass-green quartz, feebly translucent, and is sometimes covered with white or yellow spots. Plasma is somewhat lighter in weight than the heliotrope and does not take as fine a polish.

This stone is found in India, China, and in the Black Forest, Germany.

CHALCEDONY.

Chalcedony is cloudy or translucent, white, yellowish-gray, blackish-brown, light to dark-blue, milky-white, and black.

This quartz is sometimes nearly transparent, waxy in lustre, and in some varieties has a light gray and transparent base with dark cloudy spots. This last variety is called “cloudy chalcedony”. Another kind, with gray and white stripes alternating, is known as chalcedonyx.

Iceland, the Faroe Islands, Hüttenberg, Loben, Saxony, Hungary, Nubia, Nova Scotia, Oberstein, Ceylon, India, Siberia, Carinthia, the Hebrides, the United States, and Canada are places where chalcedony is found.

AGATES.

Agate is an improved variety of chalcedony and comprises the following kinds.

Banded or ribbon agate, running in delicate parallel layers.

Eye agate, forming concentric rings with a dark centre, giving the appearance of a human eye.

Fortification agate, running in circular parallel zigzag lines like the walls of a fortress.

Rainbow agate is a thin or concentric structure which when cut across and held towards the light shows an iridescence.

Moss agate, light-gray to white and translucent to opaque agates, display black tracings like fine moss or trees. Mocha or tree agates are covered with black, brown, or red figures, as of trees and plants.

Beckite or silicified coral shells, silicified wood, wood agate, wood opal, cloudy agate, and agate jasper are some of the many varieties of this class.

The common carnelians, blood-stones, and onyxes are usually counted among the agates.

Uruguay, Brazil, Oberstein, Silesia, Surinam, India, Arabia, Saxony, Scotland, the United States, and Canada are the principal places where agates are found.

ONYX OR AGATE ONYX.

Onyx is a variety of chalcedony in bands or strata of white, gray, and black, translucent to opaque, and generally found where agates abound.

The layers or bands are in even planes, and the colors, white and black, white and brown, or brown, white, and black, alternate. This stone is largely used for cameos, the base being usually of black or brown, and the engraved or upper part white- or cream-colored.

When one or more layers are of carnelian or sard, the stone is called sard-onyx. Sard is a rich brown color inclining to red, and when held against the light shows a red hue.

Onyx and sard-onyx are often artificially improved by boiling the stones in honey, oil, or sugar water, and then in sulphuric acid. The acid carbonizes the sugar or oil which the stone has absorbed and gives it a deeper color.

For red, protosulphate of iron is added, and for a blue color to imitate lapis lazuli, yellow prussiate of potash is added to the protosulphate of iron.

Only the porous parts of the stones, usually the dark parts, absorb the sugar or oil, and so aid the contrast of the colored with the white layers.

CARNELIAN.

Carnelian is a clear red translucent chalcedony, and is usually of a gray or grayish-red color. Several weeks of exposure to the sun’s rays and subsequent heating in earthen pots enhances and deepens the color.

The brownish-red or dark-brown carnelian is called sardoine or sard; the blood-red to pink varieties, with an upper layer of white onyx, are called carnelian onyx, and the stones with a brown or sard base and a white top are called sard-onyx.

Carnelians are sometimes of a yellowish-brown or yellow color, but red to brown are the principal colors.

The secret of coloring agates was discovered in the early part of this century, and about the same time agates became scarce in Oberstein, while large finds were made in Brazil and Uruguay, especially of agates with red layers. This variety comes chiefly from Brazil.

Besides Uruguay and Brazil, carnelian is found in Arabia and India. The most beautiful specimens of intaglios are engraved on sardoine, and some of the finest cameos extant are of sard and carnelian onyx.

JASPER.

Jasper is an impure opaque quartz, usually containing more iron than agate, and lacking the quality of translucency. Jasper occurs in red, brown, ochre-yellow, dark green, brownish-green, grayish-black, and grayish-blue; sometimes containing bands or spots or quartz formations, and often found with regular zones or bands of various colors.

Egyptian jasper or Egyptian pebbles are names given to varieties that are usually brown with inner bands of lighter hue, approaching cream in color, and sometimes having dark bands with spots or markings.

Egyptian jasper is found near Grand Cairo, and other varieties are found in the Urals, Saxony, Devonshire, Nova Scotia, Canada, and the United States.

The specific gravity of jasper varies from 2.31 to 2.67; it scratches glass, but yields to rock-crystal.

FALSE LAPIS.

False lapis is jasper or agate artificially colored blue to imitate the true lapis. Lapis lazuli is softer than false lapis, being only 5 to 5.5 in hardness.

Sappharine or siderite is a sapphire or sky-blue chalcedony occurring in Salzburg.

Nicolo is a variety of onyx with a black or brown base and a band or layer of bluish-white on top. The upper layer is not flat, but convex, and is always thicker than the lower one.

HEMATITE.

Hematite was once largely used to engrave upon, many of the ancient intaglios being on this mineral. It is now cut to simulate black pearls, and is also used in the cheaper jewelry, both engraved and cut cabochon.

Hematite has the hardness of 5.5 to 6.5, and specific gravity, 4.2 to 5.3; it is opaque, and shows a red streak when scratched. It is composed of:

Iron 70 Oxygen 30

The colors of hematite are dark-steel gray to iron-black, and sometimes brownish- to blood-red. The lustre is highly metallic, with slight iridescence.

The island of Elba, France, Switzerland, Italy, Norway, Sweden, Bohemia, England, Brazil, Chili, Canada, Spain, and the United States are places where hematite is found. The Germans call this mineral “blood-stone,” and it is also known as specular iron ore and iron glance.

OBSIDIAN.

Obsidian, or volcanic glass, does not occupy a high position as a gem or as an ornamental stone, but its antiquity and occasional use among the agates and semi-precious stones will justify its mention.

This mineral is a melted lava, and consists of silex, alumina, and a little potassa, soda, and oxide of iron. Obsidian is 6 to 7 in hardness, has a specific gravity of 2.25 to 2.8, is sometimes transparent but mostly translucent to opaque, and is vitreous to metallic in lustre. It is brittle and not easily attacked by acids. It melts before the blow-pipe and takes a high polish.

Obsidian comes from volcanoes, and is found in Iceland, Teneriffe, Lepare islands, Peru, Mexico, Sicily, and on all volcanoes. The color is velvety-black to gray, brown, greenish-black, yellow, blue, bottle-green, and white, seldom red, and often with black or yellow spots or veinings.

Iceland agate lava, volcanic lava, and royal agate are all obsidian.

MALACHITE.

Malachite although sometimes used for jewelry, is now more largely employed for mosaic work and ornamental vases, and is sufficiently costly and rare to be classed amongst the precious stones.

Malachite is 3.5 to 4 in hardness; has a specific gravity of 3.6 to 4; is translucent to opaque; the lustre is vitreous to adamantine. It is attacked by acids, and melts before the blow-pipe. It is composed of:

Carbonic acid 20. Protoxide of copper 71.8 Water 8.

Malachite occurs in emerald or verdigris green color, sometimes in alternating stripes of different shades of green, and occasionally in leek- to blackish-green.

Malachite is found in Russia, France, the Tyrol, England, Scotland, Ireland, Germany, Africa, Chili, Australia, and the United States.

The finest specimens are found in the Urals—a block three and a half feet square, being valued at 525,000 roubles.

JET.

The making of jet or mourning jewelry was once a very large industry in France and England, and even now Whitby jet is well known in commerce.

Jet is a species of bituminous coal (cannel coal) which can be cut with a knife. The hardness is 1 to 2.5; specific gravity, 1.35; its lustre is not very high, and color pitch-black.

It is found in England, France, Hesse, Spain, Italy, and Prussia.

AMBER.

Amber is a fossil, and is not to be classed amongst minerals, but this material has always been used as an ornament, and a few notes will not be out of place here.

This vegetable fossil, which has been known to the world for ages, the Greeks called electron.

It is very light, having a specific gravity of 1.065 to 1.08, and is 2 to 2.5 in hardness.

The principal color is yellow, in various shades, sometimes running into white or reddish-brown and black.

Amber is transparent to translucent, possesses single refraction, a resinous lustre to a high degree, becomes electric by rubbing, and burns readily before the blow-pipe.

Amber when heated becomes soft and pliable.

Amber is composed of:

Carbon 79. Hydrogen 10.5 Oxygen 10.5

Amber is imitated by gum copal, and even the insect enclosures which occur in real amber are copied.

These imitations can be detected by placing the specimen in water or alcohol. This is also a good test for pieces of real amber that have been melted or glued together.

Amber is thrown up by the sea, in rivers near the sea, or on the sea-shore, and has been found in nearly all parts of the world.

The Russian, Baltic, and Sicilian coasts have yielded the larger portion of the production, but supplies come also from Galizia, the Urals, Poland, China, and the United States.

For ornamental purposes the faceted amber beads are largely used, but of late years these have been closely imitated in glass.

CORAL.

Coral, although not a precious stone, has been largely used in jewelry, and as some of this beautiful substance is very valuable, a few words will not come amiss.

Red or precious coral is the work of a family of zoöphytes which live mostly in cavities of rock in the sea.

These polyps build their homes at a depth of two to seven hundred feet under the surface of the sea, and although the single groups of coral are sometimes several feet long, the usual size is about twelve inches high, and about one inch at the thickest part of any single branch.

Coral is usually red, and rarely white or black, while the pale rose-pink is the most esteemed color.

Coral is mostly found at Calle, off the coast of Africa, but also on the coasts of Tunis, Algiers, Corsica, Barbary, Majorca, and Minorca.

Coral fishing-vessels leave Italy the beginning of March and return from the African coast in October; at one time as many as four hundred vessels were engaged in this industry.

TABLE OF HARDNESS AND SPECIFIC GRAVITY.

────────────────────┬───────────┬────────────── │ HARDNESS. │ SPECIFIC │ │ GRAVITY. ────────────────────┼───────────┼────────────── Achroite │ 7. — 7.5 │ 3. — 3.1 Alexandrite │ 8.5 │ 3.65 — 3.8 Almandine │ 7.5 │ 4. — 4.2 Almandite │ 7.5 │ 4. — 4.2 Amber │ 2. — 2.5 │ 1.065 — 1.08 Apatite │ 4.5 — 5. │ 2.95 — 3.25 Axinite │ 6.5 — 7. │ 3. — 3.3 Beryl │ 7.5 — 8. │ 2.67 — 2.73 Bobrowska garnet │ 6. │ 3.85 Bohemian " │ 7.5 │ 3.69 — 3.78 Brazilian emerald │ 7. — 7.5 │ 3. — 3.1 " sapphire │ 7. — 7.5 │ 3. — 3.1 Cachelong │ 5.5 — 6. │ 2. — 2.1 Cat’s-eye │ 8.5 │ 3. — 3.8 Ceylon chrysolite │ 7. — 7.5 │ 3. — 3.1 " peridot │ 7. — 7.5 │ 3. — 3.1 Chrysoberyl │ 8.5 │ 3.65 — 3.8 Chrysolite │ 6.5 — 7. │ 3.3 — 3.5 Chrysoprase │ 7. │ 2.56 Cinnamon stone │ 6.5 │ 3.5 — 3.56 Cyanite │ 5. — 7. │ 3.45 — 3.7 Cymophane │ 8.5 │ 3.65 — 3.8 Demantoide │ 6. │ 3.85 Diamond │10. │ 3.5 — 3.6 Dichroite │ 7. — 7.5 │ 2.56 — 2.67 Diopside │ 5. — 6. │ 2.9 — 3.5 Emerald │ 7.5 — 8. │ 2.67 — 2.73 Epidote │ 6. — 7. │ 3.32 — 3.50 Essonite │ 6.5 │ 3.5 — 3.56 Euclase │ 7.5 │ 3.1 Fluor spar │ 4. │ 3.1 — 3.2 Garnet │ 5. — 8. │ 3.15 — 4.3 Grossularite │ 6.5 │ 3.5 — 3.56 Hematite │ 5.6 — 6.5 │ 4.2 — 5.3 Hiddenite │ 6.5 — 7. │ 3.13 — 3.19 Hyacinth │ 7.5 │ 4.4 — 4.7 Hydrophane │ 5.5 — 6. │ 2. — 2.1 Hypersthene │ 6. │ 3.3 — 3.4 Idocrase │ 6.5 │ 3.35 — 3.45 Indicolite │ 7. — 7.5 │ 3. — 3.1 Jacinth │ 7.5 │ 4.4 — 4.7 Jargoon │ 7.5 │ 4.4 — 4.7 Jasper │ 7. │ 2.31 — 2.67 Jet │ 2.5 │ 1.35 Labrador │ 6. │ 2.62 — 2.76 " hornblende │ 6. │ 3.3 — 3.4 Lapis lazuli │ 5. — 5.5 │ 2.38 — 2.42 Malachite │ 3.5 — 4. │ 3.6 — 4. Moonstone │ 6. — 6.5 │ 2.4 — 2.6 Obsidian │ 6. — 7. │ 2.25 — 2.8 Olivine │ 6.5 — 7. │ 3.3 — 3.5 Opal │ 5.5 — 6. │ 2. — 2.1 Oriental amethyst │ 9. │ 3.9 — 4.1 " aquamarine │ 9. │ 3.9 — 4.1 " chrysolite │ 9. │ 3.9 — 4.1 " emerald │ 9. │ 3.9 — 4.1 " hyacinth │ 9. │ 3.9 — 4.1 " topaz │ 9. │ 3.9 — 4.1 Pearl │ │ 2.5 — 2.7 Peridot │ 6.5 — 7. │ 3.3 — 3.5 Phenacite │ 7.5 — 8. │ 2.96 — 3. Pyrope │ 7.5 │ 3.69 — 3.78 Quartz │ 7. │ 2.5 — 2.8 " cat’s-eye │ 6. — 6.5 │ 2.65 Rose quartz │ 7. │ 2.65 — 2.75 Rubellite │ 7. — 7.5 │ 3. — 3.1 Ruby │ 9. │ 3.9 — 4.1 " cat’s-eye │ 9. │ 3.9 — 4.1 Sapphire │ 9. │ 3.9 — 4.1 " cat’s-eye │ 9. │ 3.9 — 4.1 Siberite │ 7. — 7.5 │ 3. — 3.1 Sphene │ 5. — 5.5 │ 3.4 — 3.56 Spinel │ 8. │ 3.5 — 3.6 Spodumene │ 6.5 — 7. │ 3.13 — 3.19 Star ruby │ 9. │ 3.9 — 4.1 " sapphire │ 9. │ 3.9 — 4.1 " topaz │ 9. │ 3.9 — 4.1 Sunstone │ 6. — 7. │ 2.56 — 2.72 Syrian garnet │ 7.5 │ 4. — 4.42 Titanite │ 5. — 5.5 │ 3.4 — 3.56 Topaz │ 8. │ 3.4 — 3.6 Tourmaline │ 7. — 7.5 │ 3. — 3.1 Turquois │ 6. │ 2.6 — 2.8 Uwarowite │ 7.5 │ 3.41 — 3.52 Vesuvianite │ 6.5 │ 3.35 — 3.45 Water sapphire │ 7. — 7.5 │ 2.56 — 2.67 ────────────────────┴───────────┴──────────────

GENERAL INDEX.

Achroite, 64 Actinolite, 29 Adularia, see moonstone Agate jasper, 120 Agate onyx, see onyx Agate, see quartz, 106, 119, 122, 123, 124, 126 Alexandrite, 8, 54, 56 Almandine, 9, 30, 80 Almandite, 29, 80 Amazon stone, 17, 88, 91 Amber, 17, 128 American ruby, 80, 83 Amethyst, 8, 9, 16, 17, 44, 49, 107, 110, 111 Amethystine quartz, see amethyst Antimony, 29 Apatite, 19, 87 Aquamarine, 8, 16, 53 Aquamarine chrysolite, 53 Arizona ruby, 80, 83 Asterias, see star sapphires Aurora red sapphire, see Oriental hyacinth Avanturine, 113, 114 Avanturine felspar, see sunstone Axinite, 17, 102

Balas ruby, 48 Banded agate, 119 Beckite, 120 Beryl, 14, 16, 17, 44, 50, 52, 53, 87 Blood-stone, see heliotrope " see hematite Bobrowska garnet, 80, 83 Bohemian garnet, 80 82 " diamond, see rock-crystal " topaz, see yellow quartz Bone turquois, 62 Bort, 38 Brazilian aquamarine, 85 " emerald, 64, 67 " ruby, 85 " sapphire, 85 " topaz, see topaz Bronzite, 30

Cachelong, 69, 70 Cairngorm, 107, 111 Calcite, 19 Cameo, 8 Cannel coal, see jet Cape garnet, 80, 83 Cape ruby, 80, 83 Carbon, 37 Carbonate, see carbon Carbuncle, 80 83 Carnelian, 17, 113, 123, 124 " onyx, 122 Cat’s-eye, corundum, 8, 54, 57, 115, 116 " quartz, 18, 58, 107, 113, 114, 115 Ceylon cat’s-eye, see corundum cat’s-eye " chrysolite, 64, 79 " opal, see moonstone " peridot, 64 Ceylonite, 47 Chalcedonyx, see chalcedony Chalcedony, 8, 9, 16, 17, 113, 118, 119, 120, 122, 124 Chrysoberyl, 16, 17, 45, 54, 56, 57, 79 Chrysolite, 17, 30, 53, 58, 78, 87, 99, 107 Chrysoprase, 17, 107, 113, 117 Cinnamon stone, see grossularite Cleavage, 10 Cloudy agate, 120 " chalcedony, see chalcedony Colors, 16 Coral, 130 Cordierite, see dichroite Corundum, 9, 17, 39, 45, 47, 48, 49 Crocidolite, 5, 18, 113, 115 Crystallization, 10 Cutting, 32 Cyanite, 17, 92 Cymophane, 54, 56, 57

Decimal system, 28 Demantoide, see Bobrowska garnet Diamond, 9, 11, 12, 14, 15, 17, 18, 20, 31, 32, 33, 35, 40, 41, 49, 51, 52, 60, 75, 101, 109 Dichroiscope, 14 Dichroite, 97 Diopside, 103

Egyptian jasper, 123 " pebbles, see Egyptian jasper Electricity, 31 Emerald, 8, 9, 16, 17, 18, 31, 44, 51, 87, 95, 107 Epidote, 17, 101 Essonite, see grossularite Euclase, 99 Eye agate, 119

False emerald, see fluor spar " lapis, 124 " ruby, see fluor spar " topaz, see fluor spar and yellow quartz Fancy sapphires, 44 Felspar, 20, 88, 91 Fish-eye, see moonstone Flint, 113 Fluor spar, 17, 19, 31, 104 Fortification agate, 119 Fossil turquois, 63 Fracture, 11 Fusibility, 28

Garnet, 12, 14, 15, 17, 21, 32, 42, 53, 64, 80, 107 Girasol, 46 Glass, 15 Golden beryl, 54 Goldstone, see avanturine Goutte d’eau, 85 Green felspar, see Amazon stone " garnet, 80, 99 " sapphire, see Oriental emerald Greenish-yellow sapphire, see Oriental chrysolite Grossularite, 30, 80, 82

Hair-stone, see cairngorm Heliotrope, 113, 116, 118, 120 Hematite, 18, 124 Hiddenite, 95 Hornstone, 113 Hungarian cat’s-eye, see quartz cat’s-eye Hyacinth, 42, 58, 59 Hydrophane, 69, 70 Hypersthene, 105

Iceland lava, see obsidian " spar, 14 Idocrase, 17, 98 Indian topaz, see yellow quartz Indicolite, 64, 67 Intaglio, 8 Iolite, see dichroite Iridescent quartz, see rose quartz

Jacinth, 58, 59, 82 Jargoon, 58, 59 Jasper, 17, 106, 113, 123, 124 Jet, 16, 128