488 REPORT OF NATIONAL MUSEUM, VX)0. 



l)luish, jrrayish, reddish, greenish, and green, occasional!}^ having a 

 bhiish chatoyancv or pla}' of color. 



Tlic use of this mineral for gem purposes is practicality restricted to 

 those kinds showing a bluish opalescence or play of colors, or an 

 aventurine effect, or which give a moonstone effect when cutcaljochon. 

 Prominent among the kinds affording gem material are: IVrisferite, 

 a whitish adularia-like all)ite presenting a bluish chatoyancy, usually 

 more or less mixed with pale green and yellow, the play of color 

 resembling that on the neck of a pigeon; hence the name, from 

 Ttspiorspd, pigeon. Aventurine, a grayish white to reddish gray albite 

 with internal fire-like reflections proceeding from minute disseminated 

 occluded crystals. Moo7istone, a transparent all)itc having a chatoyant 

 reflection resembling that of a cat's eye, or an opaque pearly white 

 albite having a ])hiish opalescence. 



Al])ite is a constituent of many crystalline rocks and often replaces 

 common feldspar as a constituent of granite, and is frequently a con- 

 stituent of syenite and greenstone; in other instances it is associated 

 with feldspar and dolomite. Some of the most common occuirences 

 are in veins or cavities in granite or granitoid rocks, such veins being 

 then frequently repositories of fine crystals of other gem minerals, 

 such as beryl, tourmaline, smok}^ quartz, etc. 



One hundred parts of albite contain: Silica, 68.7; alumina, 19.5; 



oda, 11.8. 



AMBER. 



SUCCINITE. 



A fossU resin occurring in irregular masses without cleavage and 

 having a conchoidal fracture. Color yellow, sometimes reddish, 

 brownish, and whitish, often clouded, and occasionally fluorescent, 

 exhibiting a peculiar blue or green tinge. Hardness 2 to 2.5; ])rittlc. 

 Specific gravity 1.05 to 1.09. Luster resinous to waxy. Transparent 

 to opaque. Negatively electrified by friction. It burns readily with 

 a rich yellow flame and aromatic odor; heated to 150° C. it begins to 

 soften and finally melts at about 250° C, giving off dense white fumes 

 having an irritating aromatic odor. It is soluble in alcohol. 



Amber contains in 100 parts: Carbon, 78.96; hydrogen, 10.51; oxy- 

 gen, 10.52. 



ANDALUSITE. 



CHIASTOLITE — MAChE. 



Andalusite has but a limited use as a gem. It crystallizes in the 

 orthorhombic system conmionly in coarse prismatic forms, the prisms 

 often nearly square; occurring also massive, columnar, radiated, and 

 granular. The color varies from a reddish or greenish brown to olive 

 green, flesh red, rose red, violet, and pearl gray; pleochroism strong 

 in some colored varieties, green in one direction and hyacinth to rose- 



