Inverell is a town in the New England region of New South Wales, Australia, and the historic centre of the New South Wales sapphire field that produced a substantial share of the world's commercial blue sapphire through the second half of the twentieth century. Together with the Anakie field in Queensland, Inverell defines Australian sapphire in the trade vocabulary, and the New England material continues to circulate even though the active mining industry there is much smaller than at its peak in the 1970s and 1980s.

Geological setting

The sapphires occur in alluvial deposits derived from the weathering of basalt flows that erupted across the New England plateau during the Tertiary. Like the Anakie material in Queensland, the New England stones are basalt-related sapphires, formed in or near magmatic processes rather than in metamorphic settings. Basalt-related sapphires worldwide, including those from Inverell, Anakie, Pailin in Cambodia and parts of Thailand, share a tendency towards strong colour saturation, frequent dark or inky tones and characteristic inclusion suites that distinguish them from metamorphic sapphires from Sri Lanka and Madagascar.

Production history

Sapphire mining at Inverell began on a small scale in the late nineteenth century but expanded substantially in the 1960s and 1970s, when alluvial workings were mechanised and Thai cutting houses took on most of the output. Through the 1970s and 1980s, Australian sapphire from the combined Inverell and Anakie fields supplied a large share of the global commercial blue sapphire market. Production has declined since the 1990s as the easily worked alluvial ground was exhausted, but artisanal and small-scale mining continues, and finished material from Australian rough still trades through Bangkok and Chanthaburi.

Visual character

Inverell sapphires tend toward dark-toned blue, often with a green or teal secondary hue and noticeable colour zoning. The classic dark Australian blue, sometimes described in the trade as inky or midnight, stems from high iron content in the basalt-related parent material. With careful cutting and selection, fine medium-toned stones occur, but the bulk of New England production is at the dark end of the saturation range. Yellow and parti-coloured (blue-yellow-green zoned) sapphires also occur and have become a recognisable Australian look in their own right.

Trade and current status

For the contemporary trade, an Inverell or New England sapphire usually enters the market as part of an estate piece set in vintage Australian or British jewellery, or as new material cut by Thai or Sri Lankan houses from old or recently mined Australian rough. Origin determination by laboratory differentiates Australian basalt-related material from Madagascan, Sri Lankan and Burmese sapphire on the basis of inclusion suites and trace-element chemistry, particularly iron and gallium ratios.