52 CONTRIBUTIONS TO MINERALOGY. [bull. 262 
BROCHANTITE. 
This basic sulphate of copper (H 6 Cu 4 SO 10 ) is usually supposed to b( 
one of the rarer minerals. It was, however, discovered at a few place? 
near Metcalf and Morenci, in well-developed crystals, and this led tc 
a systematic microscopic examination of the green ores, hitherto sup 
posed to be malachite. The result was surprising", as the mineral was 
proved to be of extremely common occurrence, mostly intergrowt 
with malachite, which had effectively masked its presence. It is 
believed that a careful examination of many so-called malachites from 
other districts will disclose the overlooked importance of brochantite 
as a copper ore. 
Brochantite is frequently crystallized in the short but stout rhombic 
prisms combined with dome and brachypinacoid characteristic of the 
species. Needle-shaped and flat crystals are more rare. The crystals 
are usually of small size and frequently microscopic. It occurs as 
lighter or darker emerald-green crusts on limonite or sericitized por 
phyry from the red ore body in the Shannon mine, from the Metcali 
mines and many other places; as fine-grained aggregates in altered 
porphyry at the Shannon mine, near the surface, constituting valiii 
able ore with as much as 30 per cent copper; from croppings of thi 
King vein, filling seams and coating porphyry fragments as flat piece * 
or even foils with almost pearly luster; from the croppings of th 
Copper Queen mine between Morenci and Metcalf, here as flat stella 
aggregates of bluish green foils; at many places near Morenci, as, fo-«. 
instance, Copper Mountain and Montezuma mines, at the latter localit 
replacing chalcocite. It would probably not be found absent froit 
any mine in the district containing oxidized copper ores. Malach'it j 
often develops later than the brochantite. 
On the whole, the mineral is most abundant in fissure veins in po j 
phyry, though also occurring in the irregular deposits in limestone. j 
Brochantite has an excellent cleavage parallel to the brachypinacoii >| 
The macropinacoid is the axial plane and the acute bisectrix is see 
emerging in cleavage foils. Pleochroism very slight. Birefringen 
much lower than malachite, about equal to that of augite. This, i 
well as the absence of twins, distinguishes brochantite from malachit 
The reaction for sulphuric acid is of course a valuable aid. 
, 
SPANGOLITE. 
This peculiar mineral (H 18 Cu 6 A1C1S0 19 ), essentially a highly basnj 
chloro-sulphate of copper and aluminum, was discovered and describ j 
by Prof. S. L. Penlicld" about fifteen years ago. The specimen cat 
from some point within 200 miles of Tombstone, Ariz., and probab 1 
a Am. Jour. ScL, ser. 3, 1890, vol. 39, pp. 370-378. 
