1042 Transactions or the American Institute. 



some period througli the rock, and deposited by tlieir concentration. 

 Clirysoprase is but an apple green chalcedony. 



The carnellan is a bright red chalcedony, of a clear, rich, flesh- 

 colored tint ; it is a great favorite of the Japanese. 



The sard is a deep brownish red chalcedony. 



Agate is a variegated chalcedony, and its colors are distributed in 

 clouds, spots or consecutive lines, which may be straight, circular or 

 zigzacr forms. When the outlines are anjrular, resembling; a fortifi- 

 cation, it is called a fortification agate ; if dendritic or moss-like 

 delineations, arising from disseminated oxyd of iron, it is called 

 mocha stone or moss agate. The color of agate is much darkened 

 b}'' boiling the stone in oil, and then dropping it into sulphuric 

 acid ; a little oil is absorbed by some of the layers and the acid 

 blackens or chars it. 



The onyx is an agate, where the colors are arranged in flat hori- 

 zontal layers, formed usually of light clear brown and an opaque 

 white. When this stone is a sard and white chalcedony in alternate 

 layers, it is called sardonyx. 



The antique cameos and sculptured small oraaments from onyx 

 are well known, such as the Mantuan vase, at Brunswick, ^even 

 inches high and two and one-half inches broad, representing a cream 

 pot, and cut from a single stone ; having white and yellow groups of 

 raised figures, representing Ceres and Triptolemus in search of 

 Proserpine, 



The cat's eye is a greenish gray translucent chalcedony, having an 

 opalescence or reflection, like the eye of a cat, when cut with a 

 spheroidal surface, probably owing to filaments of asbestos. 



The jasper is a dull red silicious rock, containing some clay, and 

 yellow or red oxyd of iron, and has all the varieties of riband, Egyp- 

 tian resin and porcelain, all assuming a high lustre and polish. 



Bloodstone or heliotrope, is of a deep green color, slightly translu- 

 cent, and containing red spots, resembling red drops of blood ; many 

 superstitious peoj^le have attached much importance to these red 

 spots, and a bust of Christ in the Paris nmseum represents quite 

 natural blood drops. 



The lydian, or touchstone, is a velvet black, silicious stone, or 

 flinty jasper, which is used on account of its hardness and black 

 color for trying the purity of the precious metals. This is done by 

 comparing the color of the tracing left on it with that of an alloy of 

 known character. 



