Sapphire in conglomerate rock

Mysteries of nature never cease to amaze us – this is a case in point from our local area.

These very heavy basalt rocks have large amounts of semi hard conglomerate rock stuck on them with a mixture of black spinel, ironstone and red ochre along with other small rocks. These are often indicators of good sapphire wash. The red ochre being common along our creek as indicated by the name of Reddestone (or Red Stone) Creek given over a century ago. Click on the photo to see a larger version.

Some history to go with this find:

This type of rock has only been found in this very localised area despite over 50 years of commercial mining in the region. This photo shows a much larger waterhole just downstream of this find – now just used for the occasional bit of fossicking and fishing – it is also a great breeding area for native wildlife.

This particular spot was one of the richest deposits of sapphire both in quality and quantity ever reported on the famous Reddestone Creek – nicknamed the “million dollar hole” indicating the richness of the wash. While working this patch, we often had to stop the plant every two to three hours to rob the jigs as the pulsators were overflowing with concentrate. Would love to see that these days !

Wash from this area was was processed through the mine plant 4-5 times and still produced viable results although the remaining stockpile of this wash contains only a small amount of this conglomerate type basalt. This wash is not viable for commercial mining but can offer great reward to the fossicker. We have spent many damp days when our black soil flats were too wet to mine the open cut holes, sitting in the shed with a hammer to break up these rocks looking for sapphire inside.

The find was in one particular hole in the creek (almost like a whirlpool) which was very deep (about 50 foot) with an almost 20 foot deep layer of wash. These particular conglomerate rocks were mainly toward the bottom and around the edge of the hole where the sapphire deposits were the richest.

We assume that the natural whirlpool location must have had a major effect on the accumulation of gems and other rocks which over time has created these basaltic conglomerate type rocks. Not being a geologist or gemmologist, this is a only guess on our part. Please contribute your thoughts as to what might have caused this phenomenon. They certainly are interesting with the added bonus of perhaps containing a valuable sapphire inside.

That is all for now from Aussie Sapphire


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