SULiMiim.s. \i;si:\ii)i:s. ANTIM<>.\II> 



ORPIMENT 



Orpiment. Arsenic trisul pi ii<le, AsjS :t ; As - <il,S =39; Mon- 

 odinic ; Type, Ditfoual Equatorial; a : b : c = .5902 : 1 : .665; 

 ft = 89 19': 110 A 110 = 62 11', 120 A 120 = 96 23'; Common 

 forms. m(110), u (120), o (101) ; Twinning plane, 100; Cleavage,b 

 perfect, lainiiue flexible, inelastic; Sectile; H. = 1.5-2; G. = 

 :i. 1 1.5; Color, lemon-yellow; Streak, pale yellow ; Luster, resi- 

 nous; cleavage surfaces pearly ; Transparent to translucent; Opti- 

 cally (); Axial plane, 001. 



B.B. Fuses and volatilizes entirely when pure, yielding an 

 arsenic odor. 



General description. Crystals are rare, but small crystals are 

 found in the clays at Tajowa, Hungary. It occurs usually in foli- 

 ated or columnar masses with rounded surfaces. It is associated 

 with and may be formed as an efflorescence on realgar. 



STIBNITE 



Stibnite. Antimony glance, Sb^s ; Antimony trisulphide ; 

 Sb_= 71.4, S = 28.6; Orthorhombic ; Type, Didigonal Equatorial ; 

 a :b: c = .9926:1: 1.0179; 100 A 110 = 44 47', 001 A 101 = 45 

 43', 001 A Oil =45 30', 111 A 110 = 34 41'; Common forms, 

 m (110), p (111), b (010) ; Cleavage, b perfect, a and m imperfect ; 

 Slightly sectile and pliable ; Fracture, conchoidal ; H. = 2 ; G. = 

 4.52-4.62; Color, steel-gray, tarnishing to black; Streak, lead- 

 gray, marks paper ; Luster, metallic, splendent on fresh surfaces. 



B.B. Fuses in O. F. at once (630) and on coal yields a white 

 coat of 80263, also an odor of sulphur dioxide. When pure, vola- 

 tilizes entirely, in R. F., yielding a yellowish green antimony flame. 

 Soluble in HC1, but in HN0 3 forms a white insoluble 



General description. Crystals are long prismatic or acicular 

 with striations and furrows parallel to the i axis, usually ter- 

 minated with the unit pyramid. Numerous forms have been de- 

 scribed, especially on crystals from Ichinokawa, Island of Shikoku, 

 Japan, where brilliant crystals nearly two feet in length have been 

 found ; in some cases these are peculiarly twisted around the vertical 

 axis. Often in radiated groups and aggregates of acicular crystals, 

 as at Felsobanya, Hungary, penetrating the tabular crystals of 

 barite with which they are associated. Massive and granular 



