Koroit Opal Field

I thought I might explain a little about the area where I mine. Koroit field has been mined at various times since the late 1800s / early 1900s. We have found tunnels on these leases down 20 ft that are only 3 to 4 feet in depth running 40 to 50 feet in different directions from a hand dug shaft. These were most likely dug with candle and pick, the miners most likely laying on their side pushing the dirt behind them - not my way of making a living. Koroit produces many types of boulder opal - the main one being boulder matrix and is world famous for this product. Matrix is where the opal is part of and runs through the ironstone making fabulous patterns and each stone is individual - you don't see two stones exactly the same. The ironstone is exactly that , very hard and takes a very good polish. The opal is found in ironstone nuts - these can be from the size of a ping pong ball up to huge in size but the average on these leases is about two tennis balls joined together and I break them with a hammer as gently as possible - you can't see any opal on the nuts so they have to be broken. As a rule the nuts are found in distinct levels but on my leases here there are no rules - the levels are all over the place, every excavator bucket has to be gone through so patience is the key. Miners do a lot of exploratory work before committing to digging an area and this is usually done over time by simple divining and using an exploratory drill to find levels - if colour comes up from a drill hole then you are feeling pretty confident that you are on a winner but there are plenty of exceptions to this theory. I have had many holes drilled here and it is a great tool for deciding where to dig and though I have found some very nice opal I have had only limited success from the drill holes. There are many different areas on Koroit field and every lease is individual in the depths of opal bearing ground as well as type of matrix opal. These leases I am working are certainly diferent to most on the field and I will endeavour to show them as time goes on.

This might do for this post so will put on some photos of the opal matrix and some other nice stones I have found here.