Stone

A Guide to Gemstones in Jewellery

Gemstones transform jewellery from metalwork into something alive with colour, light, and meaning. Each stone carries its own character — the deep blue calm of sapphire, the fiery flash of opal, the warm glow of amber. Understanding the basics of gemstone quality, hardness, and care ensures you buy pieces that look beautiful and last as long as the metal they are set in.

Precious vs Semi-Precious

The traditional precious stones are diamond, ruby, sapphire, and emerald. Everything else is classified as semi-precious — a somewhat misleading label, since stones like alexandrite, paraiba tourmaline, and black opal can be rarer and more expensive than rubies. The distinction is historical rather than qualitative. Judge each stone on its individual colour, clarity, and beauty rather than its classification.

The Mohs Hardness Scale

Hardness determines how well a stone resists scratching. Diamond is 10 (hardest). Sapphire and ruby are 9. Topaz is 8. Quartz is 7. Opal is 5.5-6.5. Pearl is 2.5-4.5. For rings (which take the most abuse), stones should be 7 or above for daily wear. Earrings and necklaces are more forgiving since they face less contact. Softer stones are fine in protective settings or for occasional-wear pieces.

Popular Gemstones and Their Qualities

Diamonds sparkle more than any other stone thanks to their refractive index — they are also the hardest. Sapphires come in every colour (not just blue) and are extremely durable. Rubies are the red variety of corundum, valued for their intense colour. Emeralds are vivid green beryl — beautiful but often included (flawed), which is accepted and expected. Opals display a unique play of colour — Australian opals are considered the finest in the world. Amethyst, garnet, topaz, and tourmaline offer excellent colour at accessible prices.

Birthstone Guide

January: garnet. February: amethyst. March: aquamarine. April: diamond. May: emerald. June: pearl or alexandrite. July: ruby. August: peridot. September: sapphire. October: opal or tourmaline. November: topaz or citrine. December: tanzanite, turquoise, or zircon. Birthstone jewellery is one of the most popular gift categories in Australia, carrying personal significance that generic jewellery lacks.

Treatments and Enhancements

Most gemstones on the market are treated. Heat treatment enhances colour in sapphires, rubies, and aquamarine — it is permanent, stable, and accepted. Oiling fills fractures in emeralds to improve clarity — standard practice. Coating and dyeing are less permanent and less accepted. Untreated stones of high quality command significant premiums. Always ask about treatments and expect honest disclosure from reputable sellers.

Caring for Gemstone Jewellery

Harder stones (diamond, sapphire, ruby) tolerate most cleaning methods including ultrasonic. Medium stones (topaz, quartz, garnet) prefer warm soapy water. Softer stones (opal, pearl, turquoise) need gentle handling — damp cloth only. Store gemstone jewellery pieces separately to prevent harder stones from scratching softer ones. Avoid exposing heat-sensitive stones (opal, pearl, amber) to sudden temperature changes.

Australian Gemstones

Australia produces some of the world’s finest gemstones. Lightning Ridge black opals are among the most valuable gemstones on earth. Queensland sapphires, particularly from the Anakie fields, produce unique dark blue and green stones. Argyle diamonds (now discontinued from the closed Argyle mine) are legendary, especially the rare pink diamonds. South Australian opals from Coober Pedy remain world-class. Wearing an Australian gemstone adds local provenance and storytelling value to your jewellery. Many Australian jewellers specialise in locally sourced stones, offering pieces with genuine geographic and cultural connection.