Potch Australian Opal | Mini
Potch is what precious opal is formed on. It can be grey, black or even white in colour. The majority of common opal mined is called Potch, so it is basically common opal with no colour. Potch is a hydrated amorphous form of silica and is known as a mineraloid. It is not classed as a mineral.
Potch mined in low depths of around 10 meters are drier than potch for the deeper underground. Potch mined down as deep as 30 meters has more loose material or chunks of opal dirt around them so it looks more like rocks with potch veins in them.
It is generally thought that if the opal miner is at shallow depths then the opal is more stable. If buyers see potch that’s full of opal dirt and if the opal dirt is muddy it tells the buyer it was mined at a lower depth. When the miner is digging in opal dirt and he finds traces of potch he will change direction and follow that vein hoping to find precious opal. It may even be on the roof of the tunnel.
When opal miners are testing a new opal field they will drill small holes in a grid formation. They are pleased to find potch as it is a good indication that precious opal is close by. If a miner finds potch it is not guaranteed that he will find precious opal.
Earthquakes or shifts in level can make many veins of potch come to a dead-end or produce no precious opal colours. If you ever get the chance to visit Lightning Ridge you will see lots of people out specking on mullock heaps after the rain. As the rain clears the dirt off the potch and if there is any opal colour exposed it is easy to see. This is called speaking similar to fossicking. People look at potch to see if any colour veins or colour flash in the piles left over from the opal mining called mullock heaps
Weight Range: Approximately 3-7g
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