Gumigil

High quality chrysoprase has been mined commercially since the 1960's, 90 kilometres north west of Rockhampton, in the Marlborough district of Central Queensland. The largest chrysoprase mine in the area is owned and operated by a Hong Kong based company Gumigil Pty Ltd. All the chrysoprase mined at the Gumigil mine is shipped to Hong Kong for processing and marketing.

The Gumigil Mine is Aslo Known as the Marlborough Chrysoprase†Mine

The Gumigil Marlborough Chrysoprase open cut mine is located 15 kilometres south of Marlborough and 165 kilometres north west of Gladstone. It is known as either the Gumigil mine or the Marlborough Chrysoprase mine.

Gumigil Mine is an Open cut Mining Operation

Chrysoprase is mined at the Gumigil mine in an open cut manner. The ore body is first ripped with a bulldozer that is followed by a person walking along behind inspecting the freshly ripped up material. This person markes out the areas where chrysoprase is exposed. The gemstone is then either picked up by hand or dug out with the aid of a backhoe. It is then taken to a screening facility where it is separated.

Chrysoprase at the Gumigil Mine Lies Under an Iron Cap

The chrysoprase and nickel-cobalt mineralisation at the Gumigil mine occurs within shears at the edges of ultramafic thrust blocks. The chrysoprase occurring in a largly saprolitic zone that can range up to 70 metres in thickness. Veins of gem quality chrysoprase sometimes reach up to eight centimetres in width. The friable nature of a rock wall containing chrysoprase allows it to be broken free with relative ease. The chrysoprase at the Gumigil mine lies beneath an iron rich cap that is sometimes 40 metres thick. The chrysoprase is found in veins in the soft, earthy clay beneath the iron crust. Then the chrysoprase is exposed the veins or nodules are removed by excavator or backhoe and the chrysoprase collected by hand. It is then cleaned under a high pressure hose and separated by wet trommelling, quality sorted and packed into drums.

Gumigil Mine Commenced Production in 1959

The Gumigil mining operation initially got underway in 1959 with two cuts being established on the one lease, the Western and the Eastern Cuts. The Western Cut has been mined out and is currently under rehabilitation. The Eastern Cut remains operational.

The Gumigil mine reached its peak production years in the 1990's. Lack of demand has reduced the amount mined in more recent years but there is still estimated to be more than 1,000 tonnes of good to medium grade chrysoprase available at the site. The Marlborough deposit of chrysoprase is the largest in Australia and generally considered to be the highest quality. Ongoing control over annual production levels is maintained to avoid the market being flooded and therefore forcing a drop in price. At current rates of production the Gumigil mine should have a life of mine for at least another 20, possibly 40 years.

Chrysoprase is the most valuable variety of microcrystalline quartz being made up of silicon dioxide. It is mainly fashioned into ornamental objects including, bangles, beads, cabochons and carved into jewellery. It is easily worked and can be highly polished.