CATALOGUE OF GEM8. 49? 



beads and other round ornaments, trinki^ts, and charms. It is also 

 made into candlesticks, paper weights, etc. 



Brown, coal is more recent in its origin than the Carboniferous period 

 of g-eologists. It sometimes closely resembles ordinary bituminous, or 

 soft coal. Other varieties have a brownish-black color, with more or less 

 of the texture of wood remaining. Often the form and fiber of the 

 original tree is retained. This variety is then called l/gnite. Brown 

 coal in some of its varieties is occasionally made into paperweights, 

 charms, and trinkets. 



COBALTITE. 



Cobaltite, when in groups or crusts of small, brilliant crj'stals, is 

 occasionally cut into ovals or other shapes and used as ring stones, 

 mountings for scarf pins, and other ornaments. Its color is pale steel 

 gray, tarnishing to copper or flesh red. Its hardness is aliout 5. 



One hundred parts contain: Cobalt, 8.5..^); arsenic, 45.2; sulphur, 19.8. 



CORUNDUM. 



KriiY SAI'l'IlIRE. 



Corundum crystallizes in the hexagonal system in six-sided prisms 

 and pyramids, the crystals often rough and rounded. Hardness 9. 

 Brittle. Specific gravity about 4, the range being from 3.916 to -1.16. 

 Luster, adamantine to vitreous; sometimes pearl}^ on the basal plane 

 and occasionalh" exhi])iting a ])right, opalescent, six-rayed star in the 

 direction of the vertical axis. The color range includes nearly all the 

 prismatic hues to colorless. Pleochroic in the strongly colored ^'arie- 

 ties. Occasionally phosphorescent, with a rich red color. 



The transparent corinidimis rank among the most valuable of gem 

 stones, and include two recognized varieties, the rub}' and the sap- 

 phire. The red-colored corundums are called rubies. They var}' in 

 hue from a rose to a deep carmine, the same crystal occasionally 

 exhibiting different colors, the most approved tint being a ''pigeon's 

 l)lood" red. The sapphire, in general, includes corundums of any 

 color except the red. Specifically, the name is limited in its usi^ to the 

 blue-colored spe(;imens, the approved tints being royal blue, \'elvet 

 blue, and cornflower blue. The sapphire occasionally exhibits a dif- 

 ferent color efl^ect ])y natural light from that seen by artificial light, 

 and as a rule is less brilliant by the latter. 



Corundums of other colors are named according to tluMr hues: Ori- 

 ental emerald, the green-colored kinds, varying in tint from a lively 

 green, exceeding that of the emerald, to a sea or bluish green. 



Oriental amethyst, purple or amethystine. Oriental topaz, yellow, 

 rivaling the yellow diamond in brilliancy. Oriental hyacinth is hya- 

 eiuthine in tint and is rare. Adamantine spar includes the hair-ln-own 

 varieties. 



The six-rayed star seen in many <'l<)uded corundums, especially when 



