332 C. H. Behre, Jr. — Native Antimony. 



apparently contemporaneous yellow or white mineral 

 thought to be valentinite. These two minerals show 

 sharp crystal faces toward each other, but ragged edges 

 against the antimony. Like the black mineral, the 

 valentinite also replaces the antimony peripherally. 

 In veins it is generally central, the black mineral more 

 nearly marginal; hence the latter is probably slightly 

 earlier. Locally the valentinite forms fissure veinlets. 

 When it and the unknowm mineral are marginal in a 

 nodule they show a cloudy suffusion, possibly represent- 

 ing a beginning alteration to a more hydrated form. 

 Wlien they are more nearly idiomorphic, the darker 

 mineral appears to be hexagonal in sections, whereas the 

 lighter one is more nearly tetragonal or may form aci- 

 cular needles or ^'barrel-shaped'' crystals like those of 

 corundum. 



Although the lighter-colored mineral yields some water 

 in the closed tube, it is thought to be valentinite (SbsOs) 

 rather than stibiconite (SbsOg.HsO), because of its 

 softness and its crystalline form. It reacts negatively 

 to the standard reagents employed by Davy and Farnham 

 for the identification of metallic minerals. In druses it 

 is crystalline; the crystals are yellowish, translucent, 

 prismatic, but poorly terminated, and lie side by side so 

 that they form a '' stockade", rather than the radiating 

 sheaf so common in stibnite ; the probability that these 

 crystals are pseudomorphs after stibnite is therefore 

 lessened. 



Both the black mineral and the valentinite are crossed 

 by veinlets which megascopically appear translucent, 

 colorless or faintly yellow, and roughly paralleling the 

 surface of the nodule. The mineral has a hardness of 5 

 and takes a good polish. Other than being slightly 

 tarnished by HCl ( ^), it shows no microchemical reaction 

 with the standard reagents of Davy and Farnham. With 

 such limited amounts observable it cannot be positively 

 identified, but it is thought to be stibiconite. In addition 

 to crossing the valentinite and the black mineral and hence 

 post-dating them in time of deposition, it may form the 

 core of such larger veins as, toward their borders, show 

 those minerals. Again, it appears to replace valentinite 

 and the black mineral in their crystalline forms, exhib- 

 iting, however, a marked preference for the latter, so 



