Zultanite (gem diaspore) crystals
as a mineralogical heritage of Turkey
Murat Hatipoglu
Dokuz Eylül University, IMYO, Izmir Multidisciplinary Vocational School,
Gemmology and Jewelry Program 35160 Buca-Izmir / TURKEY
Tel: +90-232-4400707 / 107
Fax: +90-232-4205181
E-mail: murat.hatipoglu@deu.edu.tr
Cahit Helvaci
Dokuz Eylül University, Faculty of Engineering,
Department of Geological Engineering 35160 Buca-Izmir / TURKEY
Abstract
The mineral diaspore [Al(OH)O] in itself is not rare, and is found throughout northern
and eastern Europe. However, the International Colored Gemstone Association (ICA)
declared that zultanite (gem variety of the mineral diaspore) crystals are so rare that they
worldwide are only found in Turkey. After the first modern geological studies of the
metabauxite and emery ores in the Milas (Muğla) region had been done in the early 1950s, the
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existence of diaspore crystals with orthorhombic crystalline system in the Ilbir mountains area
was discovered by chance. Therefore, they are put in relief the mineralogy importance into
geo-conservation discussion, considering as mineralogical heritage of Turkey.
The metabauxite deposit including the zultanite crystals is on the Aydın N19-a4 sheet of
the 1/25.000 scale topographic map, and is located between the Aegean sea and Bafa lake in
the Milas (Mugla) region of SW Turkey in large scale. In addition, the deposit is found in the
Kucukcamlik and Buyukcamlik hills of the Ilbir mountains area in detail.
The Milas (Muğla) region is, on the other hand, located on the southwestern section of
the Menderes crystalline massif, in which Pan-African metamorphosed and Alpine
metamorphosed rocks coexist. Thus, geological formation of the diaspore crystal-bearing
region is directly related to the geo-tectonic evolution of the Menderes massif, which can be
mostly modified by the late Alpine constructional deformation.
Zultanite crystals (Fig. 1) have vitreous striated outer surface, and some can grow to large
weights up to about 3 kg. However, average gem rough crystals are between 50-400 gr in
weight. The crystals show excellent vitreous luster even, even if they are in a rough state. This
luster is gained original appearances to the crystals for good exhibit. The unique zultanite
crystals in the Mohs’ hardness of 6.5-7 have dominantly olive green and subordinately soil
brown colorations, and display cat’s eye chatoyancy and color change as its phenomenal
properties.
In addition, no treatment is applied to induce this naturally occurring color-change. All
transparent crystals have color-change phenomenon (the alexandrite effect), such as olive
green color under direct sunlight, scattered daylight, D65 fluorescent lamp and equal energy
source E, and carmine color under low wattage tungsten, mercury and quartz lamps. However,
the phenomenon can be grouped into three color-change categories in daylight or equivalent
illuminations and low watt tungsten illuminations respectively; (1) olive green or soil
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brownish and light bordeaux, (2) olive green and lavender-rose, (3) olive green and morellocherry. As a result of these characterizations, many individual zultanite specimens and largesized gem roughs have been obtained by some famous museums and mineral collectors.
The existence of these crystals is limited because they are found in only one deposit. In
addition, the supply of the zultanite crystals are somewhat limited by difficulty of mining it.
Recovery efforts are complicated by the arduous works of separating the zultanite from its ore
matrix called diasporic metabauxite, one of the toughest industrial minerals to exploit in
mining activities. Thus, this deposit and its vicinity must be protected as a part of the
Mediterranean bauxite belt, and must be recognised in the next revision of the World Heritage
List by informing the institution ProGeo. Ultimately, these zultanite crystals of the area would
be necessary to participate in the UNESCO Global Network of geosites.
Keywords: Zultanite (Diaspore) crystals, Mineralogical heritage, Mediterranean basin, SW
Turkey.
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Fig. 1. Zultanite (gem variety of the mineral diaspore) crystals [Al(OH)O] are so rare that
they worldwide are only found in Turkey.