CompuServe Messages

Hi, Rod– (a) Cubes of quartz: pseudomorphs of quartz replacing some cubic mineral? (b) An article on calcite crystal forms in a semi-recent rockhound mag issue showed how some calcite forms could come awfully close to cubic in shape, so only a goniometer could tell it was not a true cube. Calcite is of the same rhombohedral crystal system as quartz. (c) While silicon dioxide might crystallize in the cubic system, it would not be quartz – a mineral is characterized by both a specific chemical composition and a specific crystal structure. Are we talking about a polymorph of quartz? (d) None of the above Save some cubes for me! –Doug