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Quartz Crystals – Twinning (2016)
modified: Sunday, 05-Jun-2016 02:03:08 CEST Document status: incomplete, images missing Overview of Twin TypesQuartz forms a number of different types of twins some of which are listed in the following table. Only three of them marked bold are generally accepted as twinning laws.
However, the right s-face's stripes are oriented in the same direction (not visible on the image), which would make the central face an r-face - and that can't be, except the crystal is a right/right or Dauphiné Law twin. The fingerprint-like pattern can sometimes be directly observed on rhombohedral faces of amethysts, in particular in specimen from Uruguay, but most of the times it can only be made visible by etching cross sections of crystals. 20mm 1390x930 120kb - 2780x1860 366kb Very often Japan Law twins grew in between needle quartz, like this specimen from the Mondo Nuevo Mine, Conchucos, La Libertad, Peru.
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