Glance

Glance (Ger. Glanz), a term often applied in popular language, and also by mineralogists, to a numerous order or family of minerals, of which Galena (q.v.) or Lead-glance may be regarded as a type. All of them are metallic, and many of them are known by names indicating the metal which is their principal constituent, as Lead-glance, Silver-glance, Bismuth-glance, &c. In these and many other species the metal is combined with sulphur, so that the mineral is a sulphuret; but there are also numerous species of glance in which sulphur is not present, but selenium, arsenic, or tellurium takes its place. In some kinds, also, two or more metals are present instead of one, in combination with one or other of these non-metallic or semi-metallic substances. Thus, Gold-glance, or Silvanite, consists of gold and silver in combination with tellurium; it occurs in veins in porphyry, in Transylvania, and is wrought for the sake of both the precious metals which it contains. Several kinds of glance are very valuable ores, as Lead-glance or Galena, Copper-glance or Redruthite, and Silver-glance or Argentite. Although some mineralogists have adopted the names Pyrites, Glance, and Blende as names of orders or families, the limits and distinctions of these groups are not well marked. All kinds of glance are fused without much difficulty by the blowpipe. They are also soluble in acids.