248 Reéxamination of American Minerals. 
A dark green variety gave a sp. grav. of 6°94. No analysis 
was made of this mineral, as it will be embraced in an examination 
of the American pyromorphites to be published at some future 
time. 
It is found in decomposed granite, on quartz crystals, occasion- 
ally covering their entire surface; in cellular quartz with molyb- 
date of lead; in large masses of grouped crystals with small crys- 
tals of yellow and red molybdate inserted on crystals of sulphate 
and carbonate of lead, and forming a coating to large surfaces of 
galena. 
53. Mimetene. 
The specimens of this mineral that have been found, although 
few in number, are remarkable for their beauty of crystallization. 
Some of the crystals are nearly colorless and perfectly transpat- 
ent, others of a lemon-yellow, either pure or tinged with green. 
The form is that of a perfect hexagonal prism, 2. 
the edges of the summit most commonly trun- 
cated, often to such an extent as to terminate 
the erystal with a hexagonal pyramid, ( fig. 2). 
The crystals are sometimes as small as.a hair, |. 
and a quarter of an inch or more in length, and 
ain they are so broad and short as to form 
hexagonal plates half an inch across. 
A specimen of the lemon-yellow variety was 
examined ; it gave asp. grav. of 7-32, and was 
found to contain, 
Arsenic acid, - - - ‘ - — BELT 
orine, - - - . . ‘ 2°39 
Oxyd of lead, - - - - - - 67:05 
ead, - - « = fo o 6:99 
Phosphoric acid, - - : = - re 14 
99°74 
corresponding to, Arsenate of lead 80-21, chlorid of lead 9:°38= 
Pb* As + 4PbCl 
This specimen of mimetene is seen to be almost free from phos- 
phoric acid, containing only about 7; of a per cent., in this res- 
pect resembling that from Zacatecas as analyzed by Bergmann. 
This mineral is found in granite or quartz. It is also associa- 
ted with pyromorphite and sometimes the two run together, 80 
as to present no distinct line of demarcation between them ; some 
of the specimens consist of the two minerals, the pyromorphite 
forming one entire surface, and mimetene the opposite surface, a 
between, various shades of the mixture. It has been found with 
galena and carbonate of lead. 
54. Galena. 
The compact, fibrous and crystallized varieties of galena occur 
at this mine. Fine crystals are found, either a perfect cube, cube 
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