(7) Natural Geological Specimens of Quartz and Rock Crystal. 

Condition: Commensurate with age. A few pieces show rust from being previously attached to a metal stand. 

Largest Size: 3 1/2 x 4 3/4 x 4 1/2 in. 

Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework, therefore classified structurally as a framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant of the minerals and mineral groups that compose the Earth’s lithosphere, with the feldspars making up 41% of the lithosphere by weight, followed by quartz making up 12%, and the pyroxenes at 11%. There are many different varieties of quartz, several of which are classified as gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Europe and Asia. The word “quartz” is derived from the German word Quarz, which comes from the Polish dialect term twardy meaning “hard,” combined with the Saxon word Querkluftertz, meaning cross-vein ore. The Ancient Greeks referred to quartz as krustallos, meaning “icy cold,” because some philosophers thought the mineral to be a form of supercooled ice, an idea which persisted until the 17th Century. Today, the term rock crystal is sometimes used as an alternative name for transparent coarsely crystalline quartz. Since the Industrial Revolution quartz has become more and more important to humanity outside of merely being used to make jewelry, and is now an indispensable component of most electronics around the world, with synthesized quartz emerging in the 19th Century and perfected in the early 20th. 

Commensurate with age. A few pieces show rust from being previously attached to a metal stand. 

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