Rare Turquoise from the Tosca Mine
Turquoise is extraordinarily rare in Australia. Sourced from the remote Tosca Mine, roughly 30 kilometres north of Ammaroo Station in the Northern Territory's Sandover district, this stone holds a distinct place as Australia's only known commercial turquoise deposit.
01A Unique Deposit in the Georgina Basin
While global turquoise is famously associated with the deserts of the American Southwest or ancient Persia, Australia's commercial deposits are almost non-existent. The notable exception is the Tosca Mine, located approximately 30 kilometres north of Ammaroo Station and 350 kilometres northeast of Alice Springs, in the vast arid country of the Northern Territory.
Geologically situated in the far western section of the Georgina Basin, the Tosca deposit was first formally excavated in the early 1970s, when a series of shallow open pits exposed the turquoise-bearing layers. The stone occurs as a hydrous copper aluminium phosphate, CuAl₆(PO₄)₄(OH)₈·4H₂O, forming in claystone seams between half an inch and six inches thick that sit directly over conglomerate beds and quartzitic sandstone. It precipitated near the surface through the weathering and groundwater oxidation of copper-bearing rocks, often occurring alongside malachite, chrysocolla, and montmorillonite clay.
02Ocean Blues, Sea-Greens, and Australian Lapidary
The distinctive colour palette of Tosca Mine turquoise ranges from deep robin's-egg blue to rich sea-green: a softer, greener blue than the stone most people picture. Copper ions within the chemical lattice provide the brilliant blue hues, while trace amounts of iron substituting for aluminium create the subtle green tones.
Small-scale, historical mining at Tosca yielded a mix of carving-grade material and rare, harder gem-grade specimens. Because these shallow desert seams yield thin slabs of rough, it presents a delicate lapidary challenge: at Oli&J we cut each specimen by hand into flat, low-profile geometric shapes and shallow architectural slabs suited for protective bezels and horological watch casing mounts, preserving the stone's raw, authentic matrix.
Discover Amaroo Turquoise
Explore our limited collection of rare Australian turquoise pieces, hand-cut and encased in watchmaking-grade stainless steel.
Explore the Map
