18 BULLETIN 118, UNITED STATES NATIONAL MUSEUM. 



disintegrated material of a granitic vein at Stoneham, Maine. It is 

 not much used as a precious stone and is cut chiefly as a matter of 

 scientific interest. 



LIST OF SPECIMENS. 

 UNITED STATES. 



Maine. 



Stoneham, Oxford County: 



Brilliant, square girdle ; colorless ; 5 carats; 11 by 8 mm No. 423 



Step-brilliant, square girdle; colorless; 3.86 carats; 10 by 7 mm No. 424 



Brilliant, square girdle; colorless; 3.338 carats; 9 by 7.5 mm No. 425 



Bloodstone. — See under Chalcedony. 



CALAMINE. 



Composition. — Basic zinc metasilicate (ZnOH) 2 (Si0 3 ). 



Crystallization. — Orthorhombic ; hemimorphic; habit usually co- 

 lumnar-radiated. 



Color. — White when pure, but often green or blue owing to the 

 presence of admixed copper carbonates. 



Luster. — Vitreous or somewhat silky; translucent. 



Hardness. — 5; not very durable. 



Specific gravity. — 3.45 ± 0.05. 



Optical properties. — Mean refractive index 1.62; double refraction 

 strong, 0.02; optically biaxial, positive. 



Calamine may be distinguished from most other minerals which re- 

 semble it by softness and solubility, being readily attacked by dilute 

 hydrochloric acid, with the formation of gelatinous silica. From 

 smithsonite, which is likewise attacked, it is distinguished by lack of 

 effervescence. It occurs as an alteration product of sidphide zinc ore 

 in deposits above the permanent water level and it is sometimes cut 

 cabochon and used for scarf pins, etc., but the value little exceeds the 

 cost of cutting. 



LIST OF SPECIMENS. 

 MEXICO (DISTRICT OF GALEANA, SIERRA MADRE, GUERRERO). 



Cabochon, elliptical girdle; blue clouded with white; 26.43 carats; 23 by 17 



by 12 mm. Gift of Charles H. Beers No. 1252 



Cabochon, elliptical girdle; blue banded with white; 16.49 carats; 23 by 13 



by 6.5 mm. Gift of Charles H. Beers No. 1253 



Cabochon, elliptical girdle; blue mottled with white; 10.64 carats; 18 by 



12.5 by 6 mm. Gift of Charles H. Beers No. 1254 



Cabochon, elliptical girdle; blue with curved lines of white; 8.79 carats; 



16 by 13 by 5 mm. Gift of Charles H. Beers No. 1255 



Cabochon, elliptical girdle; blue banded with white; 8.69 carats; 16 by 12 



by 5 mm. Gift of Charles H. Beers , No. 1256 



Cabochon, elliptical girdle; blue with curved lines of white; 4.825 carats; 



15 by 11 by 3 mm. Gift of Charles H. Beers No. 1257 



