fossicking and prospecting

One of my most favourite towns in the South West Corner of Queensland is Yowah and that's not just because of fossicking for opal nuts. Yowah is a great town because it has all the right ingredients. Charm, character (lots of characters) history and lots of Aussie wildlife.

Part of Yowah's charm is that it is a real outback town that lack's many of the mod-cons but you soon realize that you don't need them all anyway. All the basics are there though. Food, accommodation and of course plenty of Opal

The people in Yowah all 120 of them are as colourful as the opal they search for and they have plenty of time for a yarn. We heard some really good stories while we were there.

Yowah however is not just a place to look for opals, there are other gems in this outback Australian town. The birdlife here is amazing. The birds take full advantage of the flowing artesian water that meanders its way through the town. You will find great bird watching and photographing opportunities right in the towns parks. I counted 8 species of bird early one morning in the park next to the caravan park.

The opal in Yowah differs from the kind most people expect to see as the general public are used to the jelly or crystal opal that comes from Lightening Ridge, Andamooka and Coober Pedy. Yowah Opal in my opinion is far more interesting as it is usually banded or patterned through the matrix rock. They are called opal nuts as they typically form a spherical or oval type shape and when you cut them there are bands or layers of different minerals with the opal sometimes running through or around the matrix. Yowah opal nuts often have a lot of ironstone matrix which polishes up nicely with the opal bringing a lovely contrast.

in the old days Opal miners at Yowah were really only looking for the crystal opal in the centre of the nuts and they left behind many untracked nuts which are now highly prized in the gemstone industry.

The photograph included here is a Yowah opal nut, there is not much opal in it but it is a good example of the contrasting iron stone matrix

Once you have found some nice specimens you are going to want to clean them up and put them on display. It really depends on what you have found as what s best to do with your specimens for display. Many minerals will be part of a host rock and if you have found some with their crystal formations you will not want to break them by excessive cleaning. For some mineral types such as sulphides or hygroscopic type minerals and rocks you will want to avoid water altogether as water will start to dissolve the specimen.

On many mineral you can use a brass brush as long as the hardness of the mineral is greater than 4.5 on the Moh's scale. Dental picks for getting into crevices, ultrasonic baths, acids, sand blasting and air blasting have all been used. I have put a link on the photograph included in this section to a great website that can fill you in on the details.

There are other rocks and specimens that you will find that can be cleaned up and even polished using a tumbler polisher. Quartz based rocks or silicates with a hardness over 6 should do well. Basically any rock that has a semi shine in the natural state should polish up well. Some rocks we have successfully polished in our tumbler are Jasper, agate, chalcedony, obsidian, malachite and tigers eye.

Using a tumbler is relatively simple but it does take some time from 3 to five weeks but most of that time your machine is doing the work for you. A tumbler polishes your rocks by using abrasive grits (ground up hard rocks) of various hardness. We generally use 3 - 4 grades of grit in the process each grit running for about a week. At the end of the week we wash out the grit, clean the stones and tumbler and then add the next grade. At the end of the grits we then move onto the polishing stages.

Some things we have learned about tumbling our rocks is that you should put similar sized specimens together to tumble and similar types of rocks. Rocks with cracks or fissures will often break up in the tumbler so best to leave them out or pre cut them first. Really small specimens disappear after 3 weeks of tumbling - they become grit so don't try to polish them this way. They should be placed on dop sticks and polished by hand.

When you purchase your tumbler you will get instructions on how to use it. Don't bother with the cheap tumblers as they don't last very long. If just starting out try to get a tumbling kit that includes various grades of grit and you polish (tin oxide) so that you can get going straight away. In Australia we suggest contacting Aussie Sapphires for all your machines, grits and polish.

The photograph included here is of crocoite from Tasmania this is an example of a specimen that you would not tumble.