COPPERAS (Fr. couperose; Lat. cupri rosa. the flower of copper)

This article appears in Volume V07, Page 110 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: COM-COR

COPPERAS (Fr. couperose; Lat. cupri rosa. the flower of copper) , green vitriol, or ferrous sulphate, FeSO4.7H2O, having a bluish-green colour and an astringent, inky and somewhat sweetish taste. It is used in dyeing and tanning, and in the manufacture of ink and of Nordhausen sulphuric acid or fuming oil of vitriol (see IRON).
COPPER-GLANCE, a

mineral

MINERAL

consisting of cuprous sulphide, Cu2S, and crystallizing in the orthorhombic system. It is known also as chalcocite, redruthite and vitreous copper (German, Kupferglaserz of G. Agricola, 1546). The crystals have the form of six-sided tables or prisms; the
angle between the prism faces (lettered o in the figure) being 6o 25'. When twinned on the prism planes o, as is frequently the case, the crystals simulate hexagonal symmetry still more closely, as in the minerals arag-
onite and chrysoberyl. Twinning also takes place according to two other laws, giving rise to interpenetrating crystals with the basal planes (s) of the two individuals inclined at angles of 69 or 87 56' respectively. The

mineral

MINERAL

also occurs as compact masses of considerable extent. The colour is dark lead-grey with a metallic lustre, but this is never very

bright

BRIGHT, JOHN (1811-188g)
BRIGHT, SIR CHARLES TILSTON

, since the material is readily altered, becoming black and dull on exposure to light. The mineral is soft (H.=22) and sectile, and can be readily cut with a knife, like

argentite

ARGENTITE

; sp. gr. 5.7. Analyses agree closely with the

formula

Cu2S, which corresponds to 79.8% of copper; small quantities of iron and silver are some-times present.
Next to chalcopyrite, copper-glance is the most important ore of copper. It usually occurs in the upper part of the copper-bearing lodes, and is a secondary sulphide derived from the chalcopyrite met with at greater depths; sometimes, however, the two minerals are found together in the same part of the lodes. The best crystals are from St Just, St Ives, and Redruth in

Cornwall

CORNWALL

, and from Bristol in Connecticut. Small crystals of

recent

RECENT

formation are found on Roman bronze coins in the thermal springs at Bourbonne-les-Bains.
Copper-glance readily alters to other minerals, such as malachite, covellite,

melaconite

MELACONITE

and chalcopyrite. On the other hand, it is found as pseudomorphs after chalcopyrite, galena, and organic structures such as

wood

; copper-glance pseudomorphous after galena preserves the cleavage of the

original

ORIGINAL

mineral and is known as harrisite.
Isomorphous with copper-glance is the orthorhombic mineral stromeyerite, a

double

copper and silver sulphide, CuAgS, which occurs in abundance in the Altai Mountains. (L. J. S.)

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