Is spinel ALWAYS with sapphire?

Yes AtomRat - but I find knowledge all adds to the fun. My job sometimes leaves me alone or in small groups in the bush for weeks at a time, and I find reading local history, rocks and minerals, plants and about local people makes it more interesting (plus some fishing and 4x4 driving).

Lefty, true pyrope is Mg3Al2(SiO4)3, so it is a Mg and Al -rich mineral like some I mention above. Guess where you usually get it? In peridotites or serpentinites because they are Mg and Al-rich and low in alkalis (as soon as a rock has things like Ca and Fe in quantity, different garnets form). So expect it with sapphires and rubies (corundum) and spinel-group minerals, but not in granite-only areas. Serpentinite is usually formed by peridotite being altered by hot water, so they are similar rocks. However some pyrope also occurs in certain types of metamorphic rocks. Kimberlite that diamond occurs in is a type of peridotite that contains a special violet to purple pyrope with many percent Cr, and the presence of these in soil or streams indicates you are in a good area for diamonds (they are one of the main diamond prospecting tools, used routinely by De Beers).

You guys starting to see a pattern in all this?

So AtomRat, it is not just how they got there, but how to know where to look for them - if you like green gem garnets then look in areas with limestone next to granite (they are Ca garnets, limestone is CaCO3) - if you like orange garnets (can reach hundreds of dollars per caret), look at metamorphosed Mn layers - the orange garnets (the old name is calderite) are Mn-Ca garnets. Turquoise? Look at P-rich black slates (eg Edi in Victoria), as torquoise is a P-mineral coloured green and blue by traces of copper, which is common in very black, carbon-rich slates. And on it goes.....depends partly if you only prospect where others have found things before, or want to try new areas as well.

But even in an old area, it can help you zero in on areas close to their source, where more and larger stones may be concentrated.

WalnLiz said:

Haven't worked the Gembrook area myself but am sure Spinel and to a degree tourmaline, and weathered Olivine would be associated with the sections from which the Sapphires shed. We've found small Sapphires in the Reedy Creek area and very fine Spinel is associated with the black sands of that region as well. Many of these areas are best checked with a pan, as the Spinel is that small most falls through a 1/8" sieve. The Spinel definitely sits with the black sand and has a SG very close to Sapphire.

Send my your address via PM mate and I'll send you down some free samples of what Spinel looks like.

Wal.

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Wal, there are lots of Reedy Creeks (Beechworth, Kilmore etc). Gembrook to Beenak to upper Latrobe river good for lots of gems (see separate post), including some ruby collectted by 19th C tin miners.

My job sometimes leaves me alone or in small groups in the bush for weeks at a time, and I find reading local history, rocks and minerals, plants and about local people makes it more interesting (plus some fishing and 4x4 driving).

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Sounds like a dream job goldierocks

Yes, some basic geological knowledge can be very helpful, which is why I spend time picking the brains of geologists (actually, most of them seem to know little about gems, it isn't really their job and the ones I talk to had to pursue it as a separate area of interest).

I agree that there are virgin fields yet to be discovered in Australia, particularly among the ancient igneous formations that make up hundreds of thousands of square kilometres of ground down the eastern part of the eastern states. The vast majority of deposits will be tiny, not remotely on the scale of the Anakie or New England fields - not of all that much commercial significance but still great for fossickers. But there are probably still a few more major ones yet undiscovered.

Gemstones such as sapphires, zircons, topaz, garnets etc were all found by gold prospectors in the 1800's all up and down this region - but most of them were generally considered worthless, these blokes were after gold and pretty much nothing else. Except maybe tin (tin and topaz often go together). They were of no value to them so all that remains of the gemstone discovery knowledge of those days is a few vague and sketchy records of limited use.

So yes, arm yourself with as much geological knowledge as you can make sense of, this increases your chances.

I would rate the most important attributes as being knowledge and persistence (as well as physically fit enough to go trapsing around the countryside). What you find or don't find will not always make immediate sense.

One of the most profound pieces of ridiculously simple wisdom is one I have often heard repeated by old hillbilly-looking blokes living in tin shacks and old caravans parked in the bush of the sapphire field - the stones......are where you find them. They are spot on about that.