A gemstone or gem (also called a precious or semi-precious stone) is a piece of attractive mineral, which when cut and polished is used to make jewellery or other ornaments. They are durable and often translucent, and their attractiveness can be enhanced by polishing or faceting.
The most valuable gems are rare and provide the greatest sparkle in jewellery. These include:
- diamonds (carbon)
- sapphire and ruby (the blue and red varieties of corundum)
- emerald (the green variety of beryl)
- precious opal.
The less lustrous, semi-precious stones, which are more common in Victoria than precious stones, include garnet, topaz, turquoise and zircon.
Although many gem-grade minerals have been found in Victoria, there have been no significant commercial operations. The gemstones have been found mainly in alluvial deposits of varying ages, and less commonly in primary source rocks. Apart from opal, the precious and semi-precious gemstones commonly found in Victoria are either accessory minerals in rocks of primary igneous origin or in late-stage veins or pegmatites.
Most of the known gem minerals in Victoria were discovered during the heyday of alluvial gold mining in the 1860s and 1870s.
Although Victoria provides a rich source for a variety of polished stones and specimen minerals for fossickers, the potential for new commercial production of precious and semi-precious gem minerals is low. A possible exception to this is Beechworth diamonds, of which several hundred have been found in the Eldorado Lead along Reedy Creek. The primary hard rock diamond source has not yet been located.
- Industrial minerals and rocks of Victoria - Geological Survey of Victoria Report 102
- Gem minerals of Victoria - Mineralogical Society of Victoria
- Geological History of Victoria
- Victoria's Minerals, Petroleum and Extractives Industries - Statistical Review