MINOR GEMS. 



The stones represented in the accom- 

 panying colored plate have, for the most 

 part, but limited use, either because 

 of their local occurrence or their lack 

 of special gem qualities. Three of them 

 are peculiar to the United States, and 

 deserve on that account perhaps to be 

 better known and more widely used by 

 our people. These are variscite, chlor- 

 astrolite and thomsonite. 



VARISCITE. 



Variscite resembles turquois in many 

 properties, being, like that mineral, a gen- 

 erally opaque, hydrous phosphate of 

 aluminum not occurring in distinct 

 crystals. Its color is, however, normally 

 an apple-green to emerald-green, rather 

 than blue, and its luster is more nearly 

 vitreous than that of turquois. Its hard- 

 ness is not equal to that of turquois, be- 

 ing but 4. Its specific gravity is 2.4. It 

 is infusible before the blowpipe, but be- 

 comes white and colors the flame deep 

 bluish-green on heating. The only form 

 of it that has been used to any extent for 

 gem purposes is one recently found in 

 Cedar Valley, Toele county, Utah. This 

 is of a bright green color and occurs as 

 nodules in a crystalline limestone. Pieces 

 of this have been employed in jewelry 

 in a manner similar to turquois, though 

 the appearance of the stone is more like 

 that of chrysoprase. 



CHLORASTROLITE. 



This mineral, the name of which means 

 "green star stone," is solely of American 

 occurrence, and thus far has been found 

 at but a single locality. It occurs at Isle 

 Royale, an island in Lake Superior, in 

 the form of beach pebbles. These pebbles 

 come from the adjoining amygdaloidal 

 trap rock, out of which they weather. 

 They are opaque and of light bluish-green 

 color, with a mottled effect arising from 

 a stellated or radiated structure. This 

 structure, when the stone is polished, af- 

 fords a chatoyancy, which is very pleas- 

 ing. It is especially desirable in a good 

 stone that the radiations should emanate 

 from the center, in which case a cat's-eye 

 efTect is obtained. The pebbles which 



make good stones are mostly small, but 

 some an inch in diameter are known. 

 The hardness of the mineral is 5.5, and its 

 specific gravity 3.18. It is not a homo- 

 geneous mineral, but a mixture, composed 

 chiefly of a hydrous aluminum silicate. 

 The stones have not attained ex- 

 tensive use as yet, but are sold in quan- 

 tities to tourists in the Lake Superior 

 region. 



THOMSONITE. 



An' occurrence of this mineral which 

 is used ornamentally to some extent, is 

 obtained, like chlorastrolite, in the form 

 of waterworn pebbles weathered out of 

 an amygdaloidal trap. The pebbles are 

 found on the shores of Lake Superior, 

 near Grand Marais. They are opaque 

 and of concentric structure in layers of 

 various colors, chiefly olive-green, flesh- 

 red, cream and white. There are often 

 several centers of structure in a sin- 

 gle pebble, giving a unique and pleas- 

 ing efTect. The pebbles range up to an 

 inch in diameter and in cutting are sim- 

 ply rounded so as to best bring out the 

 various colors and centers of structure. 

 The hardness of the mineral is 5 ; speci- 

 fic gravity 2.2-2.4. Its luster is vitreous 

 to pearly. In composition it is a hydrous 

 silicate of aluminum, sodium and calcium, 

 and its occurrence is almost wholly as a 

 secondary mineral filling the cavities of 

 igneous rocks. 



While the mineral as sold at Grand 

 Marais has long been known as thom- 

 sonite, it is declared by some mineralo- 

 gists to be in reality the allied mineral 

 mesolite. 



MOLDAVITE. 



This term is applied to a transparent 

 green stone found occurring in small 

 pieces in Bohemia in the region drained 

 by the river Moldau, whence the name 

 Moldavite. The color of the stone is of 

 the peculiar character generally designat- 

 ed as bottle green, and since its physical 

 characters, such as hardness, fracture, op- 

 tical qualities, etc., also resemble those of 

 glass, the view was long held that the 

 fragments found were remains from some 



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