sii.n 'ATi:s, TITANATE8, ETC, 



B.B. Fuses with difficulty. With s<>l:i ;in<l borax in R. F. on 

 ci;il yields a zinc oxide coat. Gelatini/es with IK'I. In UK- closed 

 tube yidtls water. 



General description. Crystals MIT tabular in habit or prismatic, 

 flattened parallel to 010, with striations lengthwise. Polar in de- 

 velopment, with one end terminated by the braehydome zone, 

 while the other is termi- 

 nated by pyramids. They 

 are almost always im- 

 planted on the pyramid 

 termination, with the 

 domes free, and joined by 

 the large face 010 in paral- 

 lel positions, forming ridges 

 and crystalline crusts, with 

 a drusy surface; or in 

 nodules which show a ra- 

 diated structure when 

 broken. Simple, free crys- 



FIG. 497. Calamine from Stirling Hill, New 

 Jersey. 



tals are rare ; they occur at 

 Altenberg, in Saxony. 



It also occurs as crusts, stalactitic, mamillary, granular, or 

 earthy and amorphous ; the amorphous variety is softer than the 

 crystalline. Calamine is a secondary mineral deposited from 

 solution at low temperatures. The percolating ground waters 

 carry zinc silicate, the zinc being derived from the oxidation of 

 sphalerite which unites with the silica in solution, forming cala- 

 mine. 



Calamine is characteristic of the zone of oxidation and is asso- 

 ciated with the superficial area of most zinc deposits. Beautiful 

 specimens were formerly obtained at Stirling Hill and Franklin, 

 New Jersey. It also occurs at Friedensville, Pennsylvania ; 

 Granby, Missouri ; Virginia ; Colorado ; and Utah. 



TOURMALINE 



Tourmaline. A borosilicate of aluminium, the alkalies and 

 alkali earth metals, of the general formula RgAlstB . OH) 2 Si 4 Oi 9 , 

 in which R may be Li, K, Na, H, Ca, Fe, or Mg and Al may be 

 replaced by Fe or Cr, and OH by fluorine. The composition is 

 therefore variable, but always contains B 2 O 3 about 10 per cent., 



