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Thursday, 11 July 2013

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 Pretty Valley 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.


 There are no known basalt outcrops within 5km and the nature of this occurrence suggests that it is derived from a distinctly different source to either the Yarrow Creek or Back Creek alluvials which are the closest known sapphire deposits.

 





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).




 

Why not check out my You Tube channel here where you can view gem hunting, mining and general geology videos There are several about Pretty Valley. New subscribers are always welcome.





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