C. H. Behre, Jr. — Native Antimony. 331 



platy ; surface frequently roughened by minute parallel laminae. 

 Hardness 3.5 d= ; rather brittle. Specific gravity not determined. 

 On charcoal gives white fumes and coat characteristic of anti- 

 mony compounds ; with NasCOg yields a brittle globule of metal- 

 lic antimony. No color in beads of borax or salt of phosphorus. 

 In open tube become yellow when hot ; cools to whitish-gray slag, 

 which, in early stages of fusion, often shows minute transparent 

 crystals (senarmontite or, less probably, valentinite) ; forms very 

 slight orange-colored sublimate ( ?) and much white sublimate of 

 the usual antimony oxides. In closed tube yields slight amount 

 of II2O. In HNOg gives a white cloudy suspension (probably 

 metantimonic acid). Dissolves slowly in hot HCl; from solution 

 an excess of NH^OH throws down a heavy, white, flocculent pre- 

 cipitate. Under the microscope, polished, it is dark gray with 

 a faintly brownish tint and rough, etched surface. It reacts 

 microchemically as follows: HNO^, — fumes brown slightly, acid 

 tarnishes brown or iridescent; HCl, — fumes brown slightly ( ?), 

 acid tarnishes gray; KCN, — negative; FeClg, — tarnishes dark- 

 gray to iridescent and rubs almost clean; HgCla, — negative; 

 KOH, — roughens and tarnishes gray. 



The greater part of the coating of the nodules is 

 orange-brown and contains iron, probably in the form of 

 limonite. Elsewhere dirty olive-green shades alternate 

 with deep corn-yellow or opaque, porcellanous white ; 

 through these lighter colors undulatory lines of dark gray 

 to black can be discerned and these are readily traced to 

 veinlets that cross the nodule and native antimony core 

 and are bordered by the black, dull-luster mineral already 

 described. Scars or polished surfaces expose the tin- 

 white antimony at no great depth beneath the coat of 

 alteration products. The yellow and the white matter 

 approximate in composition valentinite or senarmonite 

 and are probably the former, as determined by qualitative 

 chemical and pyrognostic tests. 



Microscopic study reveals the following relations: 

 Five minerals are distinguishable. Of these the most" 

 conspicuous is the native metal. Rarely this shows sug- 

 gestions of radiate structure; far more commonly it is 

 merely ^ granular and massive. Neither stibnite nor 

 kermesite are associated with it, nor are there any 

 indications that it was derived from the former and tests 

 for sulphur always yield negative results. The black 

 unknown mineral replaces the native metal peripherally, 

 and occupies replacement veinlets, sharing these with the 



