HEMIMORPHITE— CALAMINE 423 



HEMIMORPHITE. 



Hemimorphite, otherwise known as electric calamine, is a hydrous silicate of zinc. It 

 sometimes occurs as colourless, transparent, rhombic crystals, but more frequently in spherical 

 or reniform shelly aggregates built up of radially arranged fibres and concentric layers. 

 These rounded masses are frequently of a beautiful bright green or blue colour, which 

 somewhat resembles that of turquoise, and, as in the latter mineral, is due to the presence 

 of a small amount of copper. They are often cut with convex surfaces and used in 

 ornamental work of various kinds. The mineral is not very durable, however, having a 

 hardness of only from 4 to 5. Its specific gravity varies from 3"35 to 3'5, so that by means 

 of these two characters hemimorphite may be readily distinguished from turquoise. Beauti- 

 fully coloured specimens are found in the zinc mines at Laurion in Attica, at Santander in 

 the north of Spain, at Nerchinsk in Siberia, and at other places ; the application of the 

 stone, however, is very limited. 



CALAMINE. 



Calamine, or zinc-spar, is carbonate of zinc, ZnCOg, and is an important ore of this 

 metal. It is found at the same localities as hemimorphite, and often occurs in the same 

 kind of aggregates, which may be bright green, blue, or even violet in colour. It is used to 

 a certain extent for ornamental purposes, the material from Laurion, in Greece, like the 

 hemimorphite from the same locality, being worked for brooches, ring-stones, and as 

 plates, &c. 



