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Thursday, 11 July 2013

PRETTY VALLEY DOG’S TOOTH SAPPHIRES

PRETTY VALLEY DOG’S TOOTH SAPPHIRES

Anyone who has hunted for gems at Pretty Valley near Glen Innes will be aware how frequently corundum crystals and hexagonal plates derived from them are found in the wash. In fact, they are more abundant here than any other place I know. We have always called them dog’s teeth; I’ve heard other call them hound’s teeth. The locality is near the source of Bladey Grass Creek.

The crystals range in size from around 0.5cm in length to over 3cm. Most are opaque and display distinct colour banding when viewed from the side. 

Transparent examples are less common and are usually yellow with a blue zone on the outside of the crystal. Doubly terminated crystals are almost unknown and the tips are usually missing. Some display crude twinning parallel to the c-axis.

The source of the PrettyValley sapphires is unknown. As usual, they are associated with abundant zircon and spinel. The schorl tourmaline, topaz and quartz crystals found there are no doubt associated with the nearby granite and are probably derived from Kingsgate-like pipes in the vicinity.
 
 
Information on the origin of sapphires in the New England region can be found in many places; the Quarterly Notes (3 and 77) of the Geological Survey of NSW contain good summaries. DIGS references for these are QN003 (1971) and QN077 (1989).


 

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