(via Wahroongai News, Volume 30, No.7, July 1996) Grahame Brown writes:
For many years I have made the general statement in lectures on synthetics that ‘blue quartz is never difficult to identify, for blue quartz does not occur naturally’. It would seem that this statement could, and should, be challenged. The reason for this change of opinion is a small paper that was published in the March-April 1996 issue of The Mineralogical Record.
The paper, titled ‘Blue quartz from the Antequera-Olvera Ophite, Malaga, Spain’, describes the occurrence of attractive dipyramidal blue quartz owing its color to aerinite inclusions.
Apparently blue quartz was first reported from the Antequera region of Spain in 1910. This deposit was rediscovered near the Olvera-Pruna road in Cadiz province—a small province that lies just to the east of the British fortress of Gibraltar. Here a clay-lined fractures in an ophitic (rock with a texture dominated by lath-shaped plagioclase crystals completely included within pyroxene) augite diabase = dolerite (a dark colored intrusive rock, containing major labradorite and pyroxene, which characteristically has an ophitic texture) rock host well crystallized dipyramidal (consisting of equally developed positive and negative rhombohedron) blue quartz crystals of 5mm to 1.5cm size.
The blue quartz crystals are actually colorless quartz crystals that are included by fibrous aerinite. These crystals vary in color from deep blue to sky blue. For the interested reader, aerinite is a monoclinic mineral that commonly adopts a fibrous habit.
Other possible causes of blue quartz are……the inclusion of colorless quartz by:
- Submicroscopic inclusions of rutile, producing a blue color in the quartz by Tyndall scattering of white light, and
- Dumortierite, a bluish to purple orthorhombic mineral.
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