Gems; Notes and ExtractsBell & Daldy, 1871 - 241 sayfa |
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acid adularia agate alabaster Alumina aluminous silicate amber amethyst amongst its varieties ancients antique aquamarina aventurine balais beautiful belong the species blow-pipe blue corundum bluish Brazil bright brilliant cacholong Caire calcareous calcedony called carats carbon carnelian century Ceylon chrysolite cleavage composed concave corundum dark diamond double refraction easily emerald engraved facets felspar France garnet gems genus glass Glucine Greek green hardness India Italy jacinth jargoon jasper kind known lapis lazuli light lime lire magnesia melts metals mineral mineralogical natural onyx opal opaque Oriental and Western Oriental ruby ornaments Oxide of iron pearls peridot plasma Pliny polish porphyry precious stones prism procured pyroxenum quartz resembles resinous rock crystal Roman rough sard scratches Siberia Silex Silex Alumina silicate sometimes specific gravity specific weight spinel spots strata substance Theophrastus tint topaz Tourmaline translucent transparent turquoise varies vitreous whence yellow دو
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Sayfa 90 - The Duke of Orleans, Regent of France during the minority of Louis XV...
Sayfa 154 - When an onyx has one or two strata of red carnelian, it is more valued and takes the name of sardonyx. In the onyx the dark strata are always opaque and contrast strongly with the clear, which, when thinned, become almost translucent.
Sayfa 31 - It crystallizes in the form of a hexagon, terminated at the two heads by a species of cone with six facets. These crystals are often in masses, and the base is always less colored than the top. Amethysts are generally found in metalliferous mountains, and are always in combination with quartz and agate. They...
Sayfa 88 - It is cut as a brilliant, and weighs 5 1 carats. nople; according to others, it ornamented the helmet of Charles the Bold, who lost it at the battle of Granson. It was found by a Swiss soldier, who sold it to a priest for two francs; it disappeared then for some time, until, in the year 1589, King Anthony of Portugal pledged it among other stones to De Sancy, then treasurer of the King of France, who retained it by paying 100,000 livres Fig. 38.— The Sancy. (coinage of Tours). Henry III., after...
Sayfa 21 - It takes a very good polish. It is never found in regular forms, but always either in nodules, in stalactites, or in irregular masses. Eye agates consist of those parts of the stone in which the cutting discovers circular bands of very small diameter arranged with regularity round one circular spot. These circles are frequently so perfect that they appear to be traced by the compass.
Sayfa 74 - One of the most beautiful qualities of the diamond is its power of refraction ; that of water is 0.785 ; ruby, 0.739; rock crystal, 0.654; and the diamond, 1.396. The refraction of the diamond is single in the entire crystals ; when broken it possesses double, but imperfect, refraction in thin layers. The value of the diamond is dependent on its color, size, and the finish or cut given during...
Sayfa 74 - ... specific gravity of the pure diamond varies from 3.5 to 3.6 ; that of the black diamond is from 3.012 to 3.255.
Sayfa 20 - ... from 2.58 to 2.69. The agate, properly so called, is naturally translucent, less transparent than crystalline quartz, but yet less opaque than jasper. It is too hard to be even scratched by rock crystal. It takes a very good polish. It is never found in regular forms, but always either in nodules, in stalactites, or in irregular masses. Eye agates consist of those parts of the stone in which the cutting discovers circular bands of very small diameter arranged with regularity round one circular...
Sayfa 151 - EYE consists of a quartz mixed with parallel fibres of asbestus and amianthus. It is found in pebbles and in pieces more or less round ; it has a concave fracture ; is translucent and also transparent at the edges. It has a vitreous and resinous light. It is generally either green, red, yellow or gray. It marks glass. Its specific gravity is from 2.56 to 2.73. When exposed to a great heat it loses lustre and transparency, but does not melt under the blowpipe unless reduced to minute fragments. Many...
Sayfa 151 - It is found in pebbles and in pieces more or less round ; it has a concave fracture ; is translucent and also transparent at the edges. It has a vitreous and resinous light. It is generally either green, red, yellow or gray. It marks glass. Its specific gravity is from 2.56 to 2.73. When exposed to a great heat it loses lustre and transparency, but does not melt under the blowpipe unless reduced to minute fragments. Many other gem stones are known to occur in the United States, and the following...