10 BULLETIN 118, UNITED STATES NATIONAL MUSEUM. 



It occurs in sediments of the later geological periods, representing the 

 fossil resin of the tree Pinvs succinifera and other plants; sometimes 

 contains insects which became embedded in the material while it was 

 soft and in a pitch-like condition. It is used chiefly for beads, ear- 

 rings, and other similar ornaments. The value of the crude material 

 is but a few cents an ounce. 



LIST OP SPECIMENS. 



COAST OF THE BALTIC SEA. 



Two cuff buttons; pale yellow; opaque No. 674 



Breastpin of 3 facetted beads and pendant; light yellow-brown No. 675 



Necklace of 50 facetted beads: light yellow-brown No. 676 



Bracelet of 16 rectangular links, 20 by 15 mm. average size, and buckle; 

 alternating pale yellow and clouded amber. Isaac Lea collection No. 1G41 



INDIA (BURMA). 



Heart-shaped cabochon; yellow-brown: S.2 carats; 20 by 7 mm No. 673 



ITALY (SICILY). 



Ten polished pieces; light and dark brown ; various sizes and shapes; total 



weight, 92.5 carats No. 671 



Pendant; brown; 19.3 carats; 45 by 18 by 10 mm. Isaac Lea collection. . No. 672 



LOCALITY NOT RECORDED. 



Necklace of 62 facetted beads, graduated sizes; yellow-brown; William H. 

 Forwood bequest No. 677 



Amethyst. — See under Quartz. 



ANDALUSITE. 



Variety. — Chiastolite or made. 



Composition. — Aluminum orthosilicate, Al 2 0(Si0 4 ). 



Crystallization. — Orthorhombic. 



Color. — Gray when pure; often showing brown-green, or yellow- 

 green, and rarely brown, pink, or violet hues, owing to the presence 

 of impurities of unknown nature ; rather strongly pleochroic, green 

 to yellow or even to red. 



Luster. — Vitreous; transparent to translucent. 



Hardness. — 7.5; a durable stone. 



Specific gravity. — 3. 20 ±0.05. 



Optical properties. — Mean refractive index, 1.64; double refraction 

 moderate, 0.01; biaxial, negative. 



Chiastolite contains symmetrically arranged carbonaceous matter 

 yielding in polished specimens a black cross on gray background. It 

 may be distinguished from tourmaline and other similar minerals by 

 its pleochroism, specific gravity, and optical properties. It occurs 

 in metamorphic rocks, especially mica schist. 



Uses. — Clear andalusite is cut facetted; chiastolite is cut cabochon 

 and used for scarfpins, and ranks as a curiosity rather than a gem. 



