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).
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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