230 - Larsen and Glenn — Minerals of the 



a = 1.531 ± 0.003. Eosine-pink (1 d) 



P = 1.549 ± 0.003. 



7 = 1.552 ± 0.003. Pale rose-pink (71 f ) 



A mineral specimen labelled bieberite (cobalt melanter- 

 ite) Bieber, Hesse, kindly fnrnished the authors by Col. 

 Roebling of Trenton, New Jersey, is a very finely 

 crystalline, rose red coating; and has the following optical 

 properties : pale rose in section, opt. — , 2V medium, 



a = 1.523 ± 0.003. p = 1.542 ± 0.005. y = 1.547 ± 0.005. 



It is probably the pentahydrate, cobalt chalcanthite, and 

 was derived from the dehydration of bieberite. 



In a desiccator over H 2 S0 4 the CoS0 4 . 6H 2 alters 

 in a few days to a mixture made up of about 80 per cent of 

 a pale rose-pink, porous pentahydrate and 20 per cent of 

 small red crystal aggregates of the monohydrate. The 

 monohydrate is in drusy crystals on the surface and in 

 the pores of the pentahydrate. The optical properties of 

 the pentahydrate are : Opt. — , 2V medium, dispersion not 

 strong, faintly pleochroic. 



a = 1.529 ± 0.003, eosine-pink (1 d) 



(3 = 1.546 ± 0.003. 



y = 1.548 ± 0.003, pale rose-pink (71 f ) 



A gram of the pale rose-pink material was hand picked 

 for water determination and gave 33.3 H 2 0. The micro- 

 scope showed that the analyzed powder contained approx- 

 imately 10 per cent of the monohydrate. This would 

 give 35.9 per cent H 2 for the pure material. The penta- 

 hydrate should contain 36.7 per cent H 2 and the rose 

 pink material is probably the pentahydrate. 



The monohydrate crystals formed with the pentahy- 

 drate have the following optical properties : Opt. — , 2V 

 near 90. Inclined extinction. 



a = 1.603. p = 1.639. y = 1.683. 



A water determination gave 11.0 per cent H 2 and shows 

 that the crystals are the monohydrate, which should con- 

 tain 10.4 per cent H 2 0. 



A solution of CoS0 4 either slightly acidified with 

 H 2 S0 4 ) or not and evaporated to dryness on a steam bath 

 gave an amaranth pink (Eidgways 6t) d) powder made up 

 of very minute crystalline spherulites and fibers with the 

 following optical properties : a = 1.600 ± 0.005, y = 1.645 

 ±0.1, elongation negative. The monohydrate is said to 



