Diamonds and pearls have been covered in previous pieces in Jeweller, so here we turn to the less celebrated, yet equally fascinating, array of secondary precious and ornamental gem materials found across the state.
Among the classic gemstones, emerald occurs in many small deposits, particularly in the Yilgarn, Murchison, and Pilbara regions, and gem-quality emeralds have been recovered from several of these localities.
Emerald is the most coveted member of the beryl group of minerals, though yellow, pink, and blue beryls are also found, with specimens only rarely of faceting quality.
In contrast to these relatively limited occurrences of classic gemstones, Western Australia hosts abundant resources of ornamental gemstone material, much of it based on quartz and other siliceous substances.
Crystallised quartz occurs in a wide range of colour varieties, from colourless rock crystal to citrine and smoky quartz, as well as amethyst in shades from lilac to deep purple, often displaying striking colour banding. Much of this material is prized by collectors as crystal specimens; however, many pieces of high quality have also been faceted.
Colourfully banded varieties of quartz and other ornamental materials are commonly tumble polished and fashioned into beads and other jewellery items.
Other decorative gemstones popular with lapidaries include varieties of microcrystalline quartz. Those with some translucency, collectively known as chalcedony, include agate, carnelian, onyx, and chrysoprase.
Of these, chrysoprase commands the highest value because of its attractive green colour, its global scarcity, and its strong demand.
Geologically, chrysoprase is a material of the regolith and is often found together with lemon and white magnesite, creating vivid combinations of colour
and pattern.
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| Western Australia’s diverse gemstone and ornamental materials represent a rich source of beautiful jewellery gemstones. |
Chrysoprase is sourced from several areas of Western Australia, particularly within the Yilgarn craton. Hard and durable, it takes a high polish.
High-quality chrysoprase from Western Australia is exported internationally, especially to Asian markets, and is used in high-end jewellery, distinctive carvings, and other objects d’art.
Iron minerals, together with secondary iron colouring in the form of patterns in many rocks, have also produced several important ornamental materials.
Mined from the vast iron-rich resources in the northwest of the state, jasper and its associated minerals provide a remarkable range of banded materials in a wide palette of colours. Well-known examples include tiger iron, tiger’s eye, zebra stone, and mookaite.
Tiger iron is a distinctive ornamental stone sourced from the Hamersley Basin. It is characterised by complex banding in brown, red, and green hues, interspersed with shimmering golden seams of tiger’s eye. These patterns make tiger iron highly sought after for jewellery and decorative purposes.
Zebra stone, from the Lake Argyle area near Kununurra, is a soft sedimentary rock consisting of extremely fine quartz particles along with mica and clay minerals.
Its matrix is whitish, with regularly distributed red-brown patches caused by enrichment with hematite. Because of its relative softness, zebra stone is generally stabilised before being fashioned into ornamental forms.
Mookaite, from the Carnarvon Basin, is a very fine-grained, fossiliferous siliceous sedimentary rock notable for its range of colours, from creams through browns to purples, and for its propensity to form fascinating patterns.
New deposits of translucent orange-red common opal, or fire opal, found in the Laverton area have provided a new source of gemstone materials. Other silica-based minerals of Western Australia also provide a host matrix for native metals, such as gold, and these materials are fashioned into attractive pendants and other decorative items.
Rounding out this short list of ornamentals is variscite. Western Australia is the only Australian state to produce significant quantities of this uncommon ornamental material.
Variscite is an attractive yellow-green to blue-green mineral, similar in colour to turquoise. The material used by the jewellery industry is sourced in the Gascoyne region, and at one location the variscite uniquely contains particles of gold. It is usually polished into cabochons together with its matrix minerals, creating striking patterns for use in jewellery.
Taken together, Western Australia’s diverse gemstone and ornamental materials represent a rich source of beautiful and interesting jewellery stones, extending far beyond the state’s better-known diamonds and pearls.
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