UNTIL recently the origin of the familiar name 'quartz' was a complete mystery. In 1942 (Min, Mag, 26, 172), Dr. S. I. Tomkeieff proposed an ingenious explantation which he now summatizes in a more recent article (Geol. Rundschau, 36, 98 ; 1948) containing a stimulating discussion of the derivations of certain old rock-names which have long resisted etymological research. Four hundred years ago, Agricola, to whom the name 'quartz' or 'quertz' was known, stated that the small veins that cross the larger metalliferous veins were called QuerJclufte by the Saxon miners. At that time the word Ertz was applied to gangue minerals, including spars, as well as to ores. Tomkeieff makes the plausible assumption that the quartz of the cross-veins of Saxony was called Querklüftertz, which in course of time became condensed to 'queretz' and 'quertz' and finally to 'quartz'. Support for this explanation comes from Cornwall, where the mineral was formerly known as 'cross course spar', a name suggesting a direct translation from Querklüftertz. 'Gneiss' or 'kneiss', also known to Agricola, has been a familiar rock-name since the days of Werner, though its origin has remained unknown. Tomkeieff learned from an old Czech miner in Joachimsthal that the country rock in which the metalliferous veins occur— the 'nest' of the ores— was called hnisto, a Czech word meaning 'nest'. The corresponding word in Russian is gnesdo, and in the other Slavonic languages it is similar. The suggestion that here we have the source of the name 'gneiss' is one that carries conviction.