THE LAVA PLAINS SAPPHIRE FIELDS
A Gemfield from Horizon to Horizon
The Lava Plains Gemfields sit at 800 to 900 meters above sea level in a northern Queensland landscape dominated by dry iron bark woodlands on shallow volcanic soils. Numerous vents and volcanic domes, and extensive basalt flows are obvious in the field.
The Lava Plains Gemfield is one of only three known economic sapphire provinces in Australia. Recent exploration has developed a new understanding of the formation processes and controls on deposits of gemstones in the area, and points to the potential for significant unexploited sapphire resources. Over several years, through its wholly owned subsidiary, the Mt Rosey Mining Company Pty Ltd, Lava Blue has secured more than 500 sq kms of exploration permits across the province, as well as the only Mining Lease in the area, giving it effective exclusive control of the entire mineral province.
Lava Blue believes that the richly mineralised province has real potential to yield other economic mineral resources in addition to the HPA, sapphires and specialty clays that it is presently commercialising.
Geology of Lava Plains Sapphire
The area was subject to several phases of volcanic activity ranging from 7 to 8 million years ago and up to possibly as recently as 15,000 years ago. The area has an unusually high number of volcanic vents and plugs, possibly as many as 100 in total across the Mt Rosey exploration permits, many of which are small and unmapped.
Older pyroclastic units from the earlier phases of volcanism appear to be the main source of sapphire as suggested by the red welded pyroclastics that have been the source of so much material won from Mines Hill and the Thai Mine Geologists have reported locally crystal rich deposits in pyroclastic units and ash beds revealed under thin basalt cover, suggesting sapphire was being found where it had been deposited after ejection from a lava tube in the early phases of volcanic activity, ie; that the sapphire at Lava Plains is being found close to the source.
It was while analysing these pyroclastic deposits for the presence of other minerals that Lava Blue realised that the volcanic ash deposits, that hosted the sapphire and had weathered to clays, are also a very rich sources of Alumina, a mineral with the same chemical formula as sapphire.
History of the Lava Plains Sapphire Province
Sapphire has been mined in the Lava Plains area since at least the 1960s.
Mechanical mining was underway by the mid-70s. Throughout the 1970s, 80s and 90s, several mines on Wyandotte Creek including Scots Mine, the Thai Mine, Mines Hill, Sapphtin, Sirls Gully, Hills Mine and other unnamed operations, collectively produced tens of millions of carats of rough sapphire exports.
In that period the Lava Plains fields became known throughout the global industry for its distinctive cobalt blue sapphire, although recent work has also recovered examples of pink, yellow, green, black and white sapphire.
By 1991 much of the Australian sapphire industry was in decline due to historically low prices as production from a rapid expansion in output from Madagascan fields was absorbed by the market. Combined with a domestic recession this lead to the Lava Plains fields being abandoned entirely until 2001, when Coolamon Mining commenced on the historical Scots Mine site.
In 2004, while digging a farm dam they discovered a previously untapped fissure from which rich sapphire grades were recovered from what is now known as Coolamon Gully. Mining continued between 2005 and 2013.
During that period, Lava Blue subsidiary, Mt Rosey Mining Pty Ltd acquired expensive exploration leases, and finally the Coolamon Mining lease itself.
Previously mined areas occupy less than 2% of the total area of the exploration permits now held by Lava Blue.
Three Sisters Volcanic Cones
Lava Plains, on the southern edge of the Undara National Park is the youngest volcanic landscape in Australia with numerous vents and volcanic features, the source of the sapphire, dominating the landscape.
Lava Plains Mined Fissure
A historically mined fissure deposit, a style of sapphire deposit unique to Lava Plains, showing the shallow depth at which concentrations are typically found and the long linear nature of the rich gemstone aggregations captured in the underlying basalt fissures.