The posted coordinates will have you standing near the Mullock heaps of the Coober Pedy public Noodling area, no permit is required to fossick here and there is no rule as to what you fossick for. Please take care in the area as the surface is uneven, there are some deep holes and the rocks can be very slippery. We have not pinpointed a specific area for you to fossick, posted Coordinates are merely a good starting point, just stay within the designated Noodling area. If you struggle to find any crystals we have note a reference point as to where we found a lot during our visit.
Whilst we tried our luck in the area noodling for Opals we were delighted to find other treasures. Perhaps not as valuable, but exciting to our Geo family just the same!
We found lots and lots of Crystals, long ones, short ones, fat ones and skinny ones. But what is it? Surely it isn’t rare with so much of it laying around; but it’s so pretty?
It is in fact Gypsum, but what is Gypsum? Gypsum is naturally occurring hydrated calcium sulphate (CaSO42H2O). Gypsum has a hardness of 2 on the Mohs scale of mineral hardness therefore is considered a soft mineral.
Gypsum’s main use is in the manufacture of plaster products including wall and ceiling boards, mouldings, and blocks for construction use, as well as sculpturing plasters, medical and dental uses and pottery. These uses rely on the relative ease with which gypsum loses and then regains its water of crystallisation. When heated to 300–350ºC, gypsum loses 75% of its H2O to form the hemi-hydrate form of calcium sulfate known as Plaster of Paris (CaSO4½H2O). When water is added, this material can be spread, cast or moulded prior to regaining its water of crystallisation and setting. Gypsum used for plaster manufacture usually contains at least 90% CaSO42H2O, a maximum of 0.02% NaCl (salt), and approximately 2% acid insolubles.
Agricultural gypsum is being increasingly used to treat sodic soils, symptoms of which are waterlogging, increased runoff, poor water storage, surface crusting, and problems with cultivation and erosion. Sodium causes swelling and dispersion of clay. The clay particles may then move through the soil, clogging pores and reducing infiltration and drainage. The calcium from gypsum displaces the sodium, which can then be leached deeper into the soil. South Australian production of agricultural gypsum exceeded 300 000 tonnes in 2002 representing a 400% increase over 8 years.
Gypsum in this geological region (termed the Eromanga Basin) is derived from two sources. Much, but not all, of it was formed in the ancient shallow seas 100 million years ago, when under conditions of high evaporation and low water circulation the combination of calcium (Ca) and sulfate (SO4) formed a relatively insoluble mineral on the sea bed. However some of the gypsum is of much more recent origin - sulfide (SO3) and sulfur (S) from the weathering Cretaceous shales (where it was formed from the decomposition of marine organisms) being oxidised to into sulfate (SO4) and combining with the ubiquitous lime (Ca) also produces the mineral.
To aide you in your search; below are some examples of the Gypsum we found:
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To log this Earth Cache we require you to find some Gypsum, consider the information given and perhaps if you need to do some research of your own, then message us with the following answers to the best of your ability;
1. How big is the piece you have found, what characteristics make you think it is Gypsum?
2. We would like you to do a little experiment, please be responsible and DO NOT DO THIS AT GZ, take a piece of Gypsum home with you (it’s ok remember this is a public fossicking area and it’s fine to take mineral samples), when you get home/back to camp, familiarise yourself with this piece, note the colour texture and density. For the next part, children please ask an adult for some help. Hold a piece with some tongs on a naked flame for 20 seconds - a minute, what happens to it? Note the changes.
3. A photo of your team or GPS near GZ or while conducting he experiment (don't put any spoilers in your photo though), upload as many photos as you like! (Optional)
You are welcome to log your answers straight away to keep your TB's and Stats in order but please message us with your answers within 24 hours. Cachers who do not fulfil the Earth Cache requirement will have their logs deleted.
**We of course want to hear if you find any Opals while you are here on your visit too, we were very lucky and found one small piece.
Source Wikipedia, Dr. Patrick Smith.
