

SE ge oe a ee 

1891.] Mineralogy and Petrography. 1007 
per Mountain Mine, near Morenci, Arizona, and from the American 
Eagle Mine, Copperopolis, Utah. In the first-mentioned locality, the 
substance forms incrustations of small, blue, fibrous tufts in a quartz 
gangue. Upon alteration it gives rise to a greenish-yellow, and finally 
to a fibrous yellowish-white material, often associated with hydrous 
aluminium sulphate. The Copperopolis specimens are velvety coatings 
of azure-blue silky fibers on a mixture of clay and lettsumite. The 
analyses of the two varieties, which are almost identical in composition, 
lead to the formula Cu,Al,(OH),,SO,+2H,O. 
SO, Cuo - ALOG -RO BO. Dba =: Sp. Ane 
12.49 46.71 16.47 1.34 21.89 44 2.737 
Crystallized metacinnabarite (which has heretofore been found 
only in amorphous masses) has recently been discovered in the New 
Almaden Mine, California. The crystals are implanted on quartz 
containing cinnabar crystals, which in turn occurs incrusting a selvage 
of clayey material forming an ore seam, whose origin is referred to 
solfataric action on the country rock. Spheres of a black organic 
substance are imbedded in the metacinnabarite, whose density is 
7-118. Its composition follows : 
S Hg Fe Co Zn Mn CaCO, Quartz Org. Matter 
13:08 Foot Or T yo -i$ 71 4.57 -63 
The crystals are rhombohedral and hemimorphic,with an acute pyram- 
idal habit, and an axial ratio a : c= 1 : .2372. In rotted galena on 
a contact between limestone and mica-schist at Mountain View Lead 
Mine, near Union Bridge, Md., Williams has found small but good 
crystals of anglesite and cerussite, and a single crystal of sulphur, all of 
which are products of the decomposition of the lead ore. The three 
principal types of the anglesite are prismatic, parallel to the brachy- 
axis, with Pz and Py predodominating, cuboidal, with Py and 
œP the principal forms, and prismatic in the direction of the 
macro-axis, with }Pz determining the habit. The cerussite presents a — 
great variety of habits. One elbow twin is peculiar in that each of the 
two individuals is bounded on the inner side by oP3, while the 
outer side contains in addition the brachy-domes }P3, Px, and 2Px. 
The sulphur crystal is very small, but it contains thirteen forms, of 
which eight are in the zone of the ground-pyramid and one $P is new. 
——The folycrase reported by Messrs. Hidden and Mackintosh ™ as oc- 
1 Melville. Ib., Oct., 1890, p. 291. 
15 Johns Hopkins Univ. Circ., No. 87. 
18 Amer. Jour. Sci., June, 1890, p. 302. 



