The Cowell Jade Province

 The following piece is by Jeff Olliver of Olliver Geological Services Pty Ltd.  He lives in South Australia (SA) and has a wealth of information and experience on the mineral resources of the state.  I met him when I was in SA recently, and he kindly agreed to share some of his experience with us.  His article follows.  I'll post a few of my pictures of Cowell jade at the bottom of this month's  blog.

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​Jeff writes: despite the use and knowledge of jade more than several thousand years ago by other civilizations, there is no record of Australian Aboriginals using it. They used other stones like agate, quartzite and sandstone.
 
Nephrite was discovered by Harry Schiller on his farm 20km north of Cowell South Australia. Harry was a mineral collector, prospector and an activist in local politics and government. He was intrigued by heavy green stones that he used to hold down fences that had been damaged by kangaroos. The specific gravity (SG) of these stones was 3.0 compared to normal rock at 2.5.
 
In late 1965, on Harry's annual trip to Adelaide, he took several samples and showed them to the Adelaide Museum, which recommended that he go to the University of Adelaide. It was morning tea and Professors and staff were in the basement tearoom of the Mawson Laboratories, named after Sir Douglas Mawson, the famous Antarctic explorer. I studied for five years to be awarded a B.Sc, followed by B.Sc(Hons). The Schiller samples were handed around. Only one unidentified lecturer said "this is going to make you a lot of money, I think it's jade"! This was greeted by laughter because there was no known jade in Australia.
 
Harry was advised to take the samples to the Department of Mines who forwarded them to Australian Mineral Development Laboratories (AMDEL). The subsequent petrological report confirmed the first record of nephrite in Australia.
 
When Don Dunstan was Premier of South Australia in early 1974, he asked the Department to investigate and determine the quantity and quality of jade at Cowell. As Senior Geologist, Mineral Resources, I supervised the field work. Detailed mapping, sampling and drilling located 120 separate outcrops, the largest was 65m by 3m and the smallest 0.2m by 0.02m scattered over an area of 5km by 2km. This was designated the Cowell Jade Province.
 
Lillian Jackson was the first lapidarist at the Kingston College of TAFE at O'Halloran Hill. She ran the jade jewellery and carving course for many years.
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Picture 1 shows four pieces of Cowell, with (clockwise from top) the first piece showing a filled fracture and what could be deformed residual bedding, the next being a lovely piece of "Black" with a minor weathering crust, the third a mid-grey-green piece with some possible residual algal detailing in the lower right, and the last showing interesting morphology suggesting irregular alteration of the host rock  

Picture  2 shows variations in a block of jade.  It has a light - mid-grey colour, possible remnant sedimentary structures and metamorphosed algal traces.  There are poorly developed black dendrites in the lower centre, caused by preferential movement of fluids containing iron or other minerals through the rock

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​Picture 3  shows a block of dark grey jade with a better-developed weathering crust (unfortunately!) containing dendrites.  The middle of the face shows some evidence of coarser crystal development

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Picture 4 shows a lovely piece of mid- to dark grey Cowell, showing only partial recrystallisation of the host rock at the bottom.  This  colour variation can be used to good effect in carvings

Picture 5 shows a beautiful piece of very fine grained mid-greyish yellow stone with a trace of dendrites at the edges and an almost buttery look

Picture 6 shows the face of a piece of jade which possibly shows the metamorphosed algal mats of the time when it was formed.  The bedding is striking!

​Picture 7 shows a beautiful piece of "Black" which has minor light grey chrystals included.  It is very fine grained and will be a wonderful stone to carve!