Sapphire from Australia

SAPPHIRES FROM AUSTRALIA By Terrence Coldham During the last 20 years, Australia has ew people realize that Australia is one of the major assumed a major role in the production of F producers of sapphire on the world market today. Yet a blue sapphire. Most of the gem material fine blue Australian sapphire (figure 1)competes favorably comes from alluvial deposits in the Anal<ie with blue sapphire from noted localities such as Sri Lanka, (central Queensland) and New England (northern New South Wales) fields. Mining and virtually all other hues associated with sapphire can be techniques range from hand sieving to found in the Australian fields (figure 2). In fact, in the highly mechanized operations. The rough is author's experience it is probable that 50% by weight of usually sorted at the mine offices and sold the sapphire sold through Thailand, usually represented directly to Thai buyers in the fields. The as originating in Southeast Asia, were actually mined in iron-rich Australian sapphires are predom- Australia. inantly blue (90%),with some yellow, some In spite of the role that Australian sapphire plays in the green, and a very few parti-colored stones. world gem market, surprisingly little has been written The rough stones are commonly heat about this indigenous gem. This article seeks both to de- treated in Thailand to remove the silk. scribe the Australian material and its geologic origins and Whileproduction has been down duringthe to introduce the reader to the techniques used to mine the last two years because of depressed prices combined with higher costs, prospects for material, to heat treat it prior to distribution, and to the future are good. market it worldwide. HISTORY The two main sources for sapphire in Australia are the New England fields, in northern New South Wales, and the Anakie fields, in central Queensland. Large-scale com- ABOUT THE AUTHOR mercial mining has been successful at these two fields Mr. Coldham is the owner of Sapphex P.L., a only. Geographically, the two areas are quite different. The Sydney-based gemstone merchant and lapidary specializing in Australian rough and cut sapphire. Anakie fields are in a semi-arid area of gently undulating Acknowledgments: The author gratefully low hills, while the New England fields cover an area of acknowledges the considerable help provided by tablelands consisting of rich grazing land and fertile river Tom Nunan (Inverell)and the Jarugosol family flats that comprise some of the best agricultural country in (Bangkok)for technical information;Gordon Streight, Dr. Brenda Franklin, and members of the Australia. Mineralogy Section of the Australian Museum for While sapphire was first reported from Inverell (NSW] proofreading and advice; Bill Scheos, Rod in 1854, the first sapphire mining started at the Anakie Brightman, Noni Primrose, and the Department of Mineral Resources (NSW) for assistance in fields almost 40 years later. In 1873, Archibald John presentation; and Sandra Pike for typing without Richardson found sapphire near the town of Anakie (Mon- complaint. teagle, 19791, about 50 km to the west of the township of Unless otherwise noted, photos are by the author. Emerald in central Queensland. Local lore has it that Em- 07985 Gemological Institute of America erald was so named because green sapphires found in the 130 Sapphires from Australia GEMS & GEMOLOGY Fall 1985 Figure 1. Twofine blue sapphires, 1.11 ct and 1.61 ct, respectively, from the New England fields, New South Wales, Australia. Photo 0 Tino Hammid. area were originally thought to be emeralds. Spo- Asia-was systematic mining resumed at Anakie. radic mining operations started in the Anakie By 1969, the Anakie fields were being fully ex- fields in the 1890s, and most of the early produc- ploited through a number of large-scale, fully tion went to tsarist Russia via German buyers. mechanized operations. Since the beginning of the The Anakie area was officially proclaimed a current decade, however, as the viable areas are mining field in 1902. Mining consisted of sinking exhausted and operating costs continue to mount, shafts or digging shallow alluvials and then wash- there has been a steady decline in production. ing the material with sieves. By 1913, two tons of Many small, semi-mechanized underground oper- sapphire and other corundum had been removed. ations now run alongside the large, heavily mech- Single pieces of gem-quality material as large as anized workings. 500 ct were reported (Anderson, 1971).Two small The second major mining field is centered villages, Rubyvale and Sapphire, appeared on the around the towns of Inverell and Glen Innes, in fields to service the miners. northern New South Wales, and is generally re- The advent of World War I, the collapse of ferred to as the New England fields. Although sap- imperial Russia, and the elimination of German phire was first found here in 1854, mining did not buyers brought mining to a virtual standstill. Not start until many years later, and even then was until the early 1960s-with the onset of a burgeon- only sporadic until 1959. As with the Anakie ing demand for rough sapphire throughout fields, the Asian buying power in the early 1960s Sapphires from Australia GEMS & GEMOLOGY Fall 1985 131 Figure 2. A miner's collection of the different-colored sapphires found at Inverell, in the New England fields, New South Wales. created favorable conditions for large-scale mech- town in Queensland and as far south as Tasmania anized mining that has continued to the present (again, see figure 3).In nearly every case, the sap- time. phires have been found in close proximity to Ce- Various attempts to mine at other localities in nozoic basalts. As mentioned above, however, in Queensland, New South Wales, and Tasmania only two areas have the deposits proved to be rich have been made, but thus far none has proved enough to allow commercial mining. viable. It is quite possible that future prospecting In most cases, the sapphire occurs in alluvial will produce new fields. gravels, termed "wash" by the miners. The gravels are associated with present-day rivers and creeks GEOLOGY in the New England region (Department of Min- All along the eastern seaboard of the Australian eral Resources, 1983), and occur as large sheets continent are scattered remnant dissected flows that cover extensive areas dissected by the present and pipes of Cenozoic volcanics (see figure 3).The drainage pattern in the Analzie fields. most common volcanic rock type is alkali basalt, The sapphire occurs as individual crystals and which in many localities contains xenocrysts of crystal fragments that in most cases have been such minerals as ilmenite, pleonaste, amphiboles, locally concentrated, presumably by normal allu- feldspar, zircon, corundum, and pyrope garnet. In vial processes. Other minerals associated with 1902, a geologist with the Queensland Mines De- sapphire are found in varying proportions and in- partment reported on the new Anakie sapphire clude (in order of abundance) pleonaste (spinel), fields, and stated that the sapphire found in the zircon, ilmenite, magnetite, olivine, pyroxenes, surrounding alluvials appeared to have been and amphiboles. Zircon is the only other mineral weathered out of the nearby basalts (Dunstan, that commonly occurs in gem quality. These zir- 1902). Since then, numerous occurrences of sap- cons are of "high type" and are either pale yellow phire have been discovered as far north as Cook- or reddish brown, ranging from sand-grain-sized 132 Sapphires from Australia GEMS & GEMOLOGY Fall 1985 particles to the occasional clear pieces of several hundred carats. Gemologically they appear to be similar to those found at the Pailin field in Cam- bodia, as described by Jobbins and Berrangd (1981). The pleonaste is usually much more abundant than the sapphire and zircon; since it has a specific gravity similar to that of sapphire, it is often used as an indicator mineral by the miner. All these minerals have been found at various localities in situ in solid basalt, pleonaste quite commonly and sapphire and zircon very rarely (McNevin, 1972). At certain localities, such as Lava Plains in northern Queensland (see figure 3), large amounts 1 of sapphire, along with pleonaste, have been found QUEENSLAND in soil directly overlying the basalts. The surfaces of material from this locality show no evidence of having traveled any distance from their source. However, while pleonaste xenocrysts are plentiful at Lava Plains, no xenocrysts of sapphire have been found in the basalt itself from which the soil ap- parently derives. Personal observations by the author show that these deposits are very similar in rock type, mode of occurrence, type of stone, and associated minerals to those found at Prae in central Thailand. Recently, quite rich deposits of sapphire were found seven miles (11 kin) east of Inverell in what appears to be pyroclastic (volcanic ash) rocks in- terbedded with basalt flows. Accessory minerals t C I are zircon and ilmenite (Lishmund and Oakes, - NEW I 1983). SOurHl WALES - In all localities, the sapphire occurs as discrete crystals and crystal fragments, often elongated * hexagonal pyramids, and occasionally bipyramids. A Almost invariably, crystal faces and fracture sur- 4 faces alike show evidence of corrosion and etching. Some crystals are so corroded that they appear as "^P^ Â¥ long cone shapes without any suggestion of their original hexagonal cross section. For quite a long 0 tat time it was thought that the material was "water worn," but it is now believed that these surfaces are a result of chemical corrosion (figure4). These 300 O- O- Figure 3. The distribution of basalts in eastern Kilometef s Australia. Major deposits of sapphire have been ----- Stale Boundaries found in the Anakie fields (Queensland)and the New England fields (NewSouth Wales).But some bsa~ sapphire has been recovered from as far north as Cooktown (Queensland) and as far south as Tasmania.

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