250 



Third Supplement to Dana's Mineralogy. 



contains selenite in large plates which are partly altered to this earthy carbonate. 

 Bischof has explained the change by supposing that waters holding carbonate of 

 soda in solution have filtrated through, producing with the gypsum sulphate of soda 

 and carbonate of lime ; but he and others have regarded the carbonate as common 

 calcite. Prof. Rose adds to the examples of the change and shows that the carbon- 

 ate is aragonite. It is generally snow-white and opaque, but minute scales are 

 transparent; and sometimes minute crystalline tables may be distinguished. These 

 tables have the form and angles of aragonite. Specific gravity 2 984 at 15° R. 



An important paper on the groupings in the twin crystals of Aragonite, Wither- 

 ite and Alstonite, by M H. de Senarmont, is contained in the Ann. de Ch. et de 

 Phys. [3], xli, 6J. The structure of the crystals was determined by means of po- 

 larized light. 



ASTROPHYLLTTE, Scheerer.~k kind of mica, from Brevig, Norway. Color 

 black and also bronze to gold-yellow ; lustre submetallic. Crystals 6-sided prisms 

 and tables, elongated in the direction of the clinodiagonal. The angle of the pmm, 

 as usual with the micas, near 120°. Lamina? but little elastic. Contains Si, 3Pe, 

 £1, Fe, Mg, K, Na, Mn, Ca, and about 3 per cent of water with no fluor. 



Atacamite(?) [p. 138, and Suppl. i]. — Prof. Scacchi questions the occurrence of 

 true atacamite at Vesuvius (op. cit., p. 197). The supposed atacamite occurs (1) in 

 slender filaments of vitreous lustre and grass green color; (2) in clustered acicular 

 opaque crystals, between brownish green and pale bluish green; (3) in an opaque 

 crust, with rough surface and emerald-green color ; (4) in a very thin crust, of a 

 fine emerald-greeii color. The first variety which seems to be the purest passes 

 into the second. 



Prof. Sc icchi concludes from his various trials, that the mineral does not contain 

 chlorine ; that its composition is not constant ; that ordinarily on immersing it in 

 water, it affords an insoluble salt of a bluish color, which dissolves in nitric acid and 

 affords reactions of sulphuric acid and copper, and may be a basic sulphate of copper. 



Binnite [Suppl. n]. — This mineral which occurs with the dufrenoysite in the dol- 

 omite of Binnen. is described by Ch. Heusser, in Pogg. xcvii, 120. Crystallization, 

 trimetric. Occurring forms prismatic, striated longitudinally, the prism 7, having 

 the acute edges replaced by ii, and the brachydomes, li, -gi, 2?, with sometimes 

 0, 1, if, and a macrodome Basal angle of the dome k% 43° 52' ; of U, 77° 32' ; of 

 §•?, 100° 38'; of 2i, 116° 12'. Color pale or dark steel-gray to black; streak- 

 powder uniformly a darker red than that of the dufrenoysite; very brittle; frac- 

 ture perfect conchoidal. 



Boa a cite [p. 393, and Suppl. n]. — The massive boracite of Stassfurt, which differs 

 from true boracite in its* ready solubility in acids, and its easier fusibility, has been 

 named Stassfurtite by G. Rose (Pogg. xcvii, 632). The solution in heated muriatic 

 acid deposits after a while, hydrated boracic acid. The masses are not properly 

 structureless but have a columnar composition and the system of crystallization 

 probably is not monometric. Chemically, boracite and stassfurtite according to the 

 analyses, give the same formula; and if so, the two are an example of dimorphism. 

 H. Rose has new analyses under way ; and other examinations of specimens may 

 clear up the doubts on the subject. 



Boron atrooalctte [p. 394]. — Analysis of this mineral from near Iquique, S. A., 

 by Rammelsberg (Pogg. xcvii, 301) : 



B* 6a fra & It 



43 70 13 11 6 67 0-83 35 67 = 100 



3 17 p. c. of chlorid of sodium, 0*41 sulphate of soda, and 0 - 39 of sulphate of lime 

 obtained in the analysis being excluded. This gives the formula Na B 2 -f-2CaB 2 -|- 

 18 H. The Hayesine, similar in physical characters, which Hayes analyzed, gave 

 him the composition CaB 2 -j-6ll. 



BRAQTTE, D. Forbes and T. Dahll (Nyt. Mag. f. Nat. xiii). — Tn indistinct, proba- 

 bly dimetric crystals, imbedded in orthoclase, and found near Helle, Naresto, Alve, 

 and Askero, Norway. Fracture uneven. H.=6— 6 5. G.=5'13— 536. Color 



