734 General Notes. 
K,O 61 11.10 
(KK. Rb.Cs),0 8.57 13.85 
Na,O 62 1.95 21 
Li,O '30 tr ‘37 5 
H,O 1.21 4.35 4.98 1.76 
Aq 2.30 1.15 1.17 
Fe <60 135 ‘19 5.68 
In the discussion which closes the paper Scharizer concludes that 
all lepidolites are isomorphous mixtures of the pure muscovite mol- 
ecule with the molecule (HO.F),. R}, Al, Si O,,.—A suite of spe- 
cimens representing the rarer copper minerals of the Mammoth 
ine region in Utah, having come into the possession of Messrs. 
Hillebrand and Washington,! an investigation of their physical and 
chemical properties was undertaken to determine their true nature. 
Measurements of the interfacial angles of olivenite from the Amer- 
ican Eagle mine yielded as the axial ratio for this mineral .9396 : 
1: .6726. It was impossible to determine whether the mineral is 
orthorhombic or not in consequence of the poor reflections from the 
æ Po faces. Olivenite from the Mammoth Mine is well crystal- 
lized, with a tabular or prismatic habit. The planes most promi- 
i “00 lo ome Pt co "Oo. “Coe ts pleochroism 
is olive-green parallel to c, and brownish yellow parallel to 6. On 
u, (AsO,). + 
H),. Two types of brochautite (hydrous sulphate of copper) 
were also examined. Crystals of the first type are dark green, ie 
are prismatic in habit. Those of the second type are of a ligh 
green color, and have a curved double-wedge shape, prone a 
the occurrence of 3 PT2 and , PQ faces. mineral with the 
general appearance of tyrolite yielded Mr. Hillebrand :— 
CuO ZnO CaO MgO AsO; P,O; HO 89s 
46.38 tr 6.69 .04 26.22 tr 17.57 2.27, 
ce = . O, 
a result indicating a composition corresponding to 5CuO. Asis 
74H,0, instead of to the generally accepted formula, 5Cu0. Ase 
O. 
light color, supposed by Mr. Pearce! to be a new mineral, has 
found upon closer examination to have the composition of Mi se 
(Cu,, Bi, As H,, Op), but different physical properties. It is 
1 Amer. Jour. Sci., xxxv., April, 1888. 
