1894.] Mineralogy and Petrography. 61 
corresponding to R,(PO,),+2 Al,(PO,),+2 Al,(OH),+21 H,O. 
eptuneite and Epididymite are associated with aegirite, arfve- 
dsonite, eudialyte, ete, near Julianehaab, Kangerdluarsuk, Green- 
land. The former is found as short, prismatic monoclinic crystals, 
with a perfect cleavage parallel to-œP. Their color is black in the 
larger crystals, but deep red brown in the small ones. Their hardness 
is 5-6, density, 3.234, and composition: 
SiO, TiO, FeO MnO MgO K,O NaO Total 
51.53 18.13 10.91 497 49 488 9.26 = 100,69 
These figures correspond to the formula (ł Na,+K,) Si,O,+(4Fe+ 
+ Mn) TiO,. Epididymite is regarded as a dimorph of eudidymite. It 
occurs in orthorhombic prisms elongated in the direction of their 
macroaxes. Their analysis: SiO, = 73.74; BeO = 10.56 Na,O = 
12.88; H,O = 3.73, corresponds to the formula for eudidymite, viz. : 
HNa Be SiO, Density = 2.548. 
Franckeite, from near Chocaya, in the Animas District, Bolivia, is an 
associate of the silver ores of the region. It occurs,” as a radial, aggre- 
gate, or as a structurelass layer of a dark gray or black substance, that 
is opaque and soft. Its hardness is about 2.75, and density 5.55. Its 
quantitative analysis yielded : 
Pb Sn Sb S Fe Zn Gangue Total 
50.57 12.34 10.51 21.04 2.48 1.22 TE BEST 
while qualitative tests showed it to contain also about .1% of german- 
iun and a fractional percentage of silver. The mineral is a sulfo-salt 
of the the formala: Pb, Sn, S, + Pb, Sb, S, It resembles in appear- 
ance and in the nature of its components the plumbo-stannite from 
Moho in Peru, but differs from it in the proportion of its constituents. 
Oylindrite owes its name to the cylindrical form that itso commonly 
assumes. It is described by Frenzel" as possessing a dark, lead-gray 
color and a metallic lustre. It is malleable, has a hardness of 2.5-3, 
and a density of 5.42. It occurs in cylindrical bodies imbedded irregu- 
larly in a granular lamellae mass of the same substance. An analysis 
of the mineral gave: 
O A Te PL Di Total 
35.41 62 8.00 8.73 26.37 2450 — 98.63 
4G. Flink, Geol. För. Férh., XV, 1893, p. 195. 
15 A. W. Stelzner, Neues Jahrb. f. Min., etc., 1893, II, p. 114. 
16 Ib., 1893, II, p. 125. 
