Australian Gem Gallery - A Rainbow of Gems

Australian Sapphires

Gem quality sapphires - blue, golden and
parti-colour from the Central 
Queensland sapphire fields

Water-worn sapphire rough

Sapphire rough and cut stones

Overview
Sapphires have been mined commercially in Australia since the late 19th century. Australia is a major producer of gem-quality sapphires and supplies a wide range of qualities and sizes of stone to world markets. The commercial mining of sapphires and the main production comes from two major fields, the Anakie field in Queensland and the New England field in New South Wales.

Australian sapphires are typical of corundum formed in iron-rich alkali basalt terrains and they have similar gemmological properties to those from other such deposits found in Thailand and Cambodia. Sapphires mainly occur in alluvial gravels, which are found in both present day streams and fossil drainage systems. Mining sapphires involves both hand mining methods and large scale open-cut operations involving the use of heavy earthmoving machinery. The sapphires are separated from the gravels by simple hand sieving and washing or processed in mechanised treatment plants.

The commercial blue stone is mainly sold under contract for export in bulk to Thailand for processing, which includes heat treatment and cutting. The smaller size stone is cut into calibrated sizes for use in the mass jewellery market. The best quality sapphires and fancy stones are supplied mainly to niche markets in Europe and the United States as well as the domestic jewellery trade and tourist market.

Queensland
The occurrence of sapphire in Queensland is widespread but deposits of commercial significance only occur on the Anakie field in central Queensland and the Lava Plains field in the north of the State.

The Anakie field which is located 43km west of Emerald covers an area of about 900km2 and includes the townships of Anakie, Sapphire, Rubyvale and Willows. This field has been the most prolific producer of sapphires in Australia and probably the world.

The smaller Lava Plains field is located 100km south of Mount Garnet and mining is centred on the Wyandotte Creek area.

Anakie
Although the first discovery of sapphire near Retreat Creek was made in the early 1870s, the first commercial mining and production did not occur until later in the early 1880s. Other mining operations began to start up in the late 1890s and by 1903 the mining of sapphires was firmly established with workings centred on two main camps to the north of Anakie, now the small townships of Sapphire and Rubyvale.

The Anakie field is large in extent and encompasses several main mining areas, including Sapphire (Big Bessie, Graves Hill, Millionaires Hill, Mount Cliffordl, Subera, Rice Bowl, New Rush, Blue Bird), Rubyvale (Scrub Lead, Bedford Hill, Normans Hill, Middle Ridge, Russian Gully, Divide, Goanna Flat), Reward (Sultana Claim, Washpool), Tomahawk Creek (Featherbed Run, Oak Flats, Zircon Gully, Ironstone Gully, Mount Hoy Diggings), Glenalva (Paceys Ridge, McAuleys Hill), Willows (Augies Gully, Rubbish Tip, Duffer, Klondyke, Thru-the-Fence, Green Ant Hill).

Today the field is characterised by mainly individual hand miners supporting the local tourist market with larger mechanised operations being undertaken by mainly small family companies or joint venture partners and only one listed public company.

The "Subera" mine to the east of the township of Sapphire is probably the largest sapphire mine in the world and production from this mine has been significant in recent years. Reportedly, nearly 2,000kg of corundum was produced in 1999/2000. Reserves contained in this vast low-grade deposit are expected to be able to support a mine life of 10 years or more.

Lava Plains
The occurrence of sapphires in the Lava Plains area was known to prospectors and fossickers for some time prior to the commencement of any commercial mining there. Some small-scale mining began in the 1970s but it was not until the mid to late1980s that large-scale mining occurred. In 1990, there were three mechanised operations in the Mines Hill-Wyandotte Creek area. Mining activity ceased in 1993 but exploration and mining tenements continued to be held over the area by a number of parties. More recently, however, there has been renewed activity on the field with testing and trial mining being undertaken there. Further development and production is likely should economic conditions prevail.

Occurrence
On the Anakie field sapphires occur in Tertiary and Quaternary alluvial deposits derived from the weathering and erosion of alkali-volcanic rocks, mainly basaltic lavas, pyroclastics and volcaniclastics of Tertiary age and underlying Palaeozoic basement rocks. The basement of the Anakie field consists of old metamorphic rocks and sediments of Late Proterozoic to Ordovician age (600 to 435 million years) known as the Anakie Metamorphics and Fork Lagoons beds, and granitoids of the Retreat Batholith which were intruded into them in Devonian times (350 to 380 million years). Although some younger sediments overlapped the area in subsequent times, little apart from erosion has occurred in this old basement block to the present day.

However, between 70 and 40 million years ago some volcanic activity erupted across the area spewing out basaltic ash and lavas. All that remains of these volcanoes now are plugs of lava that once filled their vents (eg Mount Hoy, Mount Leura); the rest having been eroded away. Referred to as the Hoy Basalt Province, it is one of many similar volcanic suites that are found throughout the highlands of eastern Australia.
It is believed that during the first phase of volcanic activity, abundant sapphires, spinels, garnets and zircons were blasted from the volcanoes as crystals in volcanic ash. Later less violent eruptions brought more normal basalt lava to the surface, carrying only a few sapphires as have been noted in the basalt at Mount Leura.

The sapphires have since been released from the volcanic material by weathering and erosion, transported by old streams, and concentrated in various layers of gravel (known as "wash") of Pliocene to Pleistocene age (2 million to 10 000 years ago). This "wash" has also been cut into by present drainage systems.

The old streams that drained the area and concentrated the sapphires in bed and bank deposits flowed towards the north and northeast, generally parallel to, and in some cases co-incident with modern streams. The sapphires and other heavy minerals tended to be concentrated in "runs" along particular channels in the old watercourses (palaeodrainage system). In some areas, the presence of several "wash" layers indicates the filling of channels with barren sediments and later deposition of sapphire-bearing material over the top.
The wash so formed is termed "high level wash", and occurs above present stream levels. It is variable in thickness and depth, reflecting original topographic features, and has undergone varying degrees of consolidation. Degradation of this wash by erosion, in places by gravity acting down-slope, and elsewhere by water, has formed areas of secondary "lower level wash". Modern streams have also reworked older wash deposits leading to sapphires in their drainages.

The Lava Plains field lies within one of several major basalt provinces in northeastern Queensland, the McBride Basalt Province. There are many volcanic vents ranging in size from large shield volcanoes to smaller pyroclastic and scoria cones. The oldest rocks are Tertiary to Quaternary basalts which comprise the greater part of the province and have ages between 2.7 and 0.5Ma. Many other younger Quaternary lava flows from various craters in the area make up the other units. It appears that the sapphires are associated with older eruptive volcanics from a limited number of vents and are found in the eluvium, colluvium and alluvium within and adjacent to present day watercourses in the vicinity of these vents. The sapphires occur mainly in shallow clayey soils along with abundant vesicular basalt rock fragments and basalt cobbles and boulders.

New South Wales
Sapphires occur at many different localities in New South Wales with stones having been recovered from mainly alluvial deposits and deep leads. In 1851, during gold mining on the Cudgegong and Macquarie Rivers in central New South Wales the discovery of sapphires there were first reported.

Most of the commercial mining of sapphires and production has come from the New England region in the north east of the State. The New England field is centred around the townships of Inverell and Glen Innes where both past and present mining activity is located in several main areas, including Swan Brook, Frazers Creek, Horse Gully, Wellingrove Creek, Reddestone Creek and Kings Plains Creek.

Inverell-Glen Innes
The first commercial mining of sapphires on the New England field commenced in 1919 at Frazers Creek near Inverell. Rich alluvial deposits in streams were worked initially by hand miners but there was little recorded production up to about 1960. During the late 1960s, Thai gem buyers began buying sapphire in quantity and a boom resulted with the number of small operations increasing dramatically. The depletion of these easily worked, shallow alluvials and subsequent decline of production led to the search for new deposits.

The search of the alluvial valleys in the district resulted in new deposits and mines, including "Braemar" near Elsmore, "Warrandah" near Kings Plains and "Strathdarr" south of Warrandah. Mining commenced at Narran Vale in 1995 and operations ceased in mid 1998. Reportedly, some 6,045kg of sapphire were produced in 1996 and 1997. Production from the Strathdarr mine (Western Feeder Production Joint Venture) for the three years up to June 1997 was just over 9,000kg. The Warrandah mine began production in 1998 following the closure of Narran Vale but the mine ceased operations in early 2001. Recorded production for the period 1998/2000 was 5,642kg. The new Weean mine, which began limited production in 2001 is a large resource and the operators expect it will replace production capacity lost following the closure of Warrandah. Several other potential new deposits and mines in the area are being assessed for future development, including Kings Plains Creek (Vivers), Yarrandoo, Rose Hill, Quantum, Rutherglen, Inverell, Frazers Creek, Beardy Waters and Reddestone 2.

Small private companies and joint venture partners largely undertake today's sapphire mining. Systematic exploration in the New England has enabled more efficient mining and increased production from existing mines as well as the discovery of new deposits for future mining. Remaining resources appear sufficient to maintain production levels with new mines starting up as others close down once economic resources are depleted

A large proportion of sapphires produced from this field is sold under contract to overseas buyers, the bulk of which goes to Thailand.

Occurrence
The rocks of the New England field comprise Tertiary basaltic volcanics, intrusives and sediments of the Central Volcanic Province which overlie and intrude Devonian-Triassic metasedimentary, volcanic and plutonic basement rocks of the Central Block of the New England Fold Belt.

At Inverell-Glen Innes, sapphires typically occur in Quaternary and Tertiary alluvial deposits in both present day drainages and fossil drainage systems. The sapphire-bearing gravel layer ('wash') varies in thickness but may be up to a few metres in some palaeo-alluvial channel systems. Most of the sapphires are found in Holocene alluvial deposits of post-volcanic drainages or intra-volcanic alluvial deposits in sediments sandwiched between basalt lava flows. It is thought that most of the sapphire was derived from the weathering and erosion of sapphire-bearing volcanic ash deposits (volcaniclastic rocks) that were erupted onto the earth's surface prior to the lava flows. Sapphire has also been won from weathered primary volcanic rocks in a layered volcaniclastic sequence.

Gemmological properties of Australian sapphires

Mining and Processing
The methods employed by the early sapphire miners were largely of a manual nature using simple hand tools. Surface or shallow deposits were hand raked with material being either hand picked or processed by dry or wet sieving on the spot to separate out any sapphires. Sieving involves the separation and removal of the coarse and fine fraction of the 'wash' and the concentration of the heavy minerals including sapphires by gravity from the retained material.

Hand mining methods were also used to work the deeper ground, shafts were sunk to locate the gravel layer ('wash') which was systematically removed by driving (tunnelling) from the bottom of the shaft. The excavated material was loaded into a bucket and hoisted to the surface with the aid of a windlass. The gravel layers vary from only a few centimetres to metres in thickness. The miners tested ground and traced the gravel layers by sinking test shafts but the layers were often erratic or discontinuous and not all were sapphire bearing. Some miners thought that once the clay layer was encountered this meant the bottom but it was soon discovered that in some areas a 'false bottom' existed and there was another deeper gravel layer below before the true basement was reached.

Today's hand miners employ the same basic techniques used by the early miners. Although underground mining is still widely practised in Queensland, miners are able to use certain powered machinery approved under State mining laws. On a mining claim, machinery that can be used is limited but may include a jack-pick and bucket hoist. Mechanical diggers, bobcats and tunnelling machines and such like are not allowed.

The excavated material is hoisted to the surface where it is treated by rudimentary hand sieving or in small powered washing and separation equipment using basic gravity methods to separate any sapphires. The concentrate is later sorted by hand.

Large scale open-cut operations use heavy earthmoving machinery to remove overburden and mine the gravel layer. Material is processed in mechanised plants, which may be smaller mobile plants or larger plants with high tonnage throughput capacity to concentrate the heavy minerals including the sapphires. The wash is transported by truck from the mine site and dumped into a large bin from which it passes through a trommel (rotating coarse/fine screens) to separate it into different sizes and remove oversize material. Material is then passed into a pulsator (pulsating jig) to concentrate the heavy minerals by gravity separation. The lighter materials are washed out of the pulsator as tailings whilst the heavy minerals including sapphires are retained by the riffles in the jigs Additional screens and jigs may be added to the processing circuit to treat different wash types. Further processing of the concentrate may involve additional sieving to separate the various size groups and passing the material through a powerful magnetic separator to remove ironstone and other magnetic minerals. The retained concentrate comprising corundum (gem sapphire and non-gem corundum) and zircon is given a final wash before sorting and grading ready for market.

Earlier attempts to value-add product in Australia have only met with limited success. The bulk of commercial stone is still sent offshore for routine heat-treatment and cutting. Other better quality stone, including yellow, green, parti-colour and fancy stone is largely supplied to the domestic jewellery trade and tourist market as well as niche markets overseas. Stone has been processed in Sri Lanka and Thailand under joint-venture arrangements and it is highly likely that such arrangements will continue because of the lower labour costs and established facilities.

Conclusion
Australia's sapphire production has decreased significantly since the late 1980s when it produced about 70% by volume of the world's sapphire. Although production remains at historically low levels, the demand on international markets for Australian sapphires remains high. Today the commercial mining of sapphires continues in Queensland and New South Wales, and although further production from remaining resources on these fields can be expected, new deposits will be needed for the future. Continued exploration and testing of new areas may locate additional resources, which is vital for future mining and production.

The industry faces increased competition from other sapphire producing countries but much of this continues to be sporadic. In recent years, however, there have been increases in production costs for miners as well as difficulties with access to new ground for exploration and mining. Miners are held responsible for the environment and environmental conditions for their mining operations including rehabilitation of the land must also be met. Further development of marketing strategies and value-adding opportunities is essential to ensure the industry remains viable.

Further Reading
Department of Mineral Resources, Sydney., 1995: Sapphires in New South Wales (booklet).

Scholler, W. L., 1985: Anakie the sapphire fields of central Queensland - Australia. Published by E & W Scholler, 2nd Edition 1986; 3rd Edition 1990.

Scholler, W. L., 1993: Images of the Anakie sapphire fields - Queensland. Anakie, Australia. Published by E & W Scholler.

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