526 The American Naturalist. [June, 
been gathered by Luck," who has made an extensive crystal- 
lographic and chemical study of them. Coquimbite is declared 
to be rhombohedrally hemihedral with a \ c = i : 1.56 13. 
Its hardness is 2 — 2.5 and specific gravity =r 2.079 — 2. 114. 
Copiapite has been determined to be monoclinic with a\b\c = 
.4791 : I : .9759 and /9_== 71'' 56'. The mineral cleaves par- 
allel to coPoo'and \ Poo. Its hardness is 2.5 and specific 
gravity 2.103. Analysis yielded : 
SO3 Fe.Oa Ae.O, CaO H,0 
38.91 .^o.ii tr. 30.74, corresponding to 
Fe, (HO), (SO,), + 18 Aq. Stypticite occurs in radially fibrous 
aggregates of a yellowish-green color. Its hardness is 2.5 
and specific gravity 1.857. Its crystalization is probably 
monoclinic. Its composition was found to correspond to 
Fe, (OH), (SO.), + 9 Aq. Upon alteration it gives rise to a 
grayish-yellow substance what is probably identical with 
fibto ferrite. Tabular crystals of romerite and found to be 
triclinic with a : b : c = .9681 : i : 2.6329 and oc = 1 16"" 2' : 
,9 = 940 41' : r = 80^ 8'. Its cleavage is basic, hardness 3 
and specific gravity 2.102. An analysis of pure material leads 
Linck to regard the mineral as Fe (Fe Al), (SOJ, + 15 Aq. 
Chilian halotrichite yielded on analysis : 
SO, AeA PeA FeO CaO MgO H,0 
33-98 10.43 -95 5-55 .69 .78 46.94 
Among these sulphates is one occuring in reddish-violet, tab- 
ular crystals, in habit resembling gypsum crystals. It is 
monoclinic with a : b : c = .3942 : i : :4o6o. /9 = ^7° 58'- 
Most of the crystals are elongated in the direction of the clino 
diagonal. The plane of the optical axes is in 00?^^' and the 
first bisected is inclined to c in the obtuse angle ^. The 
the double refraction is negative, hardness 2.5, specific gravity 
2.1 155. Its composition is 
SO, Fe.Os Al,03 CaO MgO H,0 
39.83 27.66 tr. .40 tr. 31-35 
corresponding to Fe, (SO,), -h 10 Aq. The author calls the 
mineral qiienstedite.Some interesting pyrite crystals are de- 
scribed by Mr. W. B. Smith' from the mines in Gilpin and 
Summit counties, Colorado. The crystals from the Saratoga 
mine in the former county are remarkable for the large num- 
'ZeitsJ. Kryst.xv. p.i. 
