Current Notes on Mineralogy, Lithology, and Metalliferous Deposits

H. C. Salmon
1860 The Geologist  
The October number of the "Philosophical Magazine" contains a notice, translated from Poggendorff's "Annalen," by Professor Gustav Rose, on the isomorphism of stannic, silicic, and zirconic acids. Stannic acid (n) forms the mineral Cassiterite, silicic acid (i) is Quartz, zirconic acid, which Rose considers to be r, has hitherto been classed as an earth or oxide, as zirconia, with composition r, or r. The mineral zircon, hitherto held to be a silicate of zirconia, must now, according to this,
more » ... ccording to this, be merely considered as an isomorphous compound of one atom of zirconic acid and one atom of silicic acid ( r + i). This mineral species has always been remarkable for the variation of hardness and gravity in specimens from different localities, which according to this hypothesis may be accounted for by the unequal proportions of the two acids; the heavier and harder specimens containing the more zirconic acid, whose equivalent would be 481·20 compared with 384·888 that of silica. In the case of a variety found in Russia by Hermann, composed of two atoms of r, with three atoms of i (r2 i3), the specific gravity was only 4·06, while that of the mineral of the ordinary composition varies from 4·5 to 4·8.
doi:10.1017/s1359465600020311 fatcat:bwy4so77t5bqpku3vpxsl4jd5e