Vivid Violet Sugilite: A Rare Precious Stone

Write By: tmmadmin Published In: Mineral Species Created Date: 2016-06-23 Hits: 6645 Comment: 0

 

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Specimen photos©TreasureMountainMining.com   


INTRODUCTION
Gem sugilite is a polycrystalline aggregate: a massive gem material that is colored a very attractive purple-violet color, due to the presence of manganese. It is named for Ken-ichi Sugi, the Japanese geologist who discovered it in 1944 on an island in Japan. This material bears no resemblance to the gem grade purple sugilite that was found in 1979 at the Wessels Mine in South Africa. There was some controversy about the true identity of this material, which was originally thought to be sogdianite, but was soon shown to contain a small amount of manganese and no zirconium, and was thus proven to be the rare mineral sugilite. It is also known as lavulite.

 

Note: Most people pronounce sugilite with a soft "g" sound, as in "ginger". The correct (but rarely heard) pronunciation is with a hard "g" as in "goose", after the name of the discoverer, Sugi.


COLOR
Sugilite's most recognizable feature is its color, which is a rich, saturated, deep dark purple. It can also range in color from pink to lilac to lavender, and from plum to magenta, and reddish- or bluish-purple. The distinctive purple color is due to the presence of about 1-3% manganese (in the form of manganoan oxide) in its chemical structure. The color may be uniform, but can also show up in veins, layers, or blotchy patches. For jewelry, a uniform reddish-purple is the most desirable color. Sugilite is usually opaque, with a waxy luster, but can be translucent in thin sections.


CHARACTERISTICS
There are two types of sugilite found at the Wessels Mine: The first is relatively pure sugilite, and the other contains varying amounts of chalcedony mixed in, though its properties are so similar that it is indistinguishable without testing with x-ray diffraction or other studies. Viewed under a microscope, sugilite is seen to contain interlocking crystal grains of less than 1 mm in diameter - a structure that is referred to as polycrystalline.

 

Sugilite is KNa2(Fe,Mn,Al)2Li3Si12O30, a sodium-potassium-lithium cyclosilicate. It has good to excellent toughness, with no observed cleavage. It has a hardness of 5 to 6; similar to apatite to feldspar, it can be scratched with a nail or steel file. Its specific gravity is 2.7, similar to aluminum. Its crystal system is hexagonal. It does not fluoresce. The primary structural unit of sugilite is a most unusual double ring, with a formula of Si12O30. Normal rings of cyclosilicates are composed of six silicate tetrahedrons; Si6O18. The double ring is made of two normal rings that are linked together by sharing six oxygens, one from each tetrahedron in each six membered ring (notice the loss of six oxygens in the double ring formula). The structure is analogous to the dual wheels of a tractor trailer and is shared by other members of the Milarite - Osumilite Group.

Dark purple sugilite that is translucent and has a grape jelly color is called "gel sugilite", and is so rare that it is extremely expensive and sold by the carat.


GEOLOGY
In South Africa, sugilite formed deep in the earth in beds of manganese-rich metamorphic rocks that are the remains of magma. These are the strata-bound manganese deposits are mined in the Kalahari manganese deposits at the Wessels and other mines in Northern Cape Province of South Africa. They are the largest, richest manganese deposits in the world. The Wessels mine is an underground mine, exploiting layers of enriched manganese ores that are 5 to 25 meters thick, with purities of up to 50%. These layers of manganese ore, which were derived from either weathering or from hydrothermal solutions associated with invading magmas, were deposited in a sedimentary basin between 2.6 and 2 billion years ago. Sugilite is found in seams up to 15 cm thick within certain zones in the manganese ore. The sugilite layers can run for up to 15 meters, but are not continuous. They also occur in space-filling patches between broken blocks of manganese ore. Associated minerals include braunite, acmite, andradite, wollastonite, pectolite, vesuvianite, glaucochroite, and quartz.


MINING
Sugilite was discovered at the Wessels Mine by accident, when a sugilite-rich area was encountered during normal mining operations.
It is mined using hand tools, then brought to the surface where it is separated from manganese ore for separate sale.

In 1975 a larger deposit of gem grade sugilite was found in another area thousands of feet below the original discovery. The part of the mine where the sample was obtained contained only low grade ore, so excavation of this area did not ensue until several years later, after the high grade areas had been mined. In 1979 miners turned their efforts to the low grade ore area where the Sugilite had been found. At 3,200 feet below the surface, an inclined shaft's roof fell in, exposing the first major deposit of gem grade sugilite. This great pocket yielded about ten thousand pounds of material suitable for gem making. Most of this original material has since been used up, but occasionally more was found, but in limited quantities. It is not known to occur at any of the other manganese mines in the area. 


USES
Sugilite is popular in jewelry, in thin sections which can be polished or cut into cabochons and mounted in silver or gold in rings, pendants, and earrings. In the 1980s the gem was heavily promoted on home shopping channels and internet auctions sites.


TREATMENT
There are no known treatments for sugilite that enhance its appearance, color, or translucency. Imitation plastic sugilite is known and is used in cheap jewelry, but it is a poor substitute.  


HISTORY
The mineral sugilite was first discovered in 1944 on Iwagi Islet in southwest Japan by the Japanese petrologist Ken-ichi Sugi (1901–1948).
On Iwagi Islet it occurs in limited amounts as small brownish yellow grains in an aegirineic syenite host rock.


Sugilite from Iwagi Islet in Japan


Sugilite was first described by Muralzami et al. in 1976. After it was discovered in South Africa in 1979, it was officially classified as a rare gem in 1980, which caused its price to increase. Also in 1980, it was reported as a few tiny pink crystals in manganese ore from the state of Madhya Pradesh in India, which had been mined in 1955 but not tested (only a single dark red ore specimen was found). In the early 1980s, sugilite was marketed under tradenames such as "Royal Hazel", "Wesselite" and "Lavulite", but none of these caught on.

By the mid-1990s, known reserves at the Wessels Mine were exhausted, and no additional material has been found since. In recent years, high demand for sugilite in China exhausted stock from most mineral dealers, and prices escalated rapidly. By 2015 it had become nearly impossible to find any sugilite specimens at other than ridiculously high prices.

In 2013, a small find at the Wessels Mine produced well-crystallized specimens. This new material occurred in masses of hair-like crystals in thin veins only, but sugilite crystals are even rarer than the massive material, so this was a very important discovery.  Specimens that were found featured colorful, bright lavender sugilite in fibrous crystals with a silky sheen. These fibrous crystals are the rarest form of crystallized sugilite. Here are some examples:




OTHER OCCURRENCES
Besides South Africa, Japan, and India, sugilite has been found at Mont Saint-Hilaire, Quebec, Canada. It is also reported from Liguria and Tuscany, Italy; New South Wales, Australia. The deposits in South Africa are by far the largest and are the only ones that are economically important.


METAPHYSICS
Sugilite, which has been called a "new age stone", is associated with the zodiac signs Pisces, Sagittarius, and Aquarius. It is said that sugilite strengthens the heart, aids physical healing and reduces stress. It is a balancer of mind, body and spirit and encourages peace of mind, a general feeling of well-being and spiritual love. It is also suggested that sugilite seems to protect against and dissipate anger and other negative energies.


People interested in metaphysics and crystal healing tell us that sugilite is a love stone for this age, representing the perfection of the spiritual love of all that is. Sugilite stimulates the heart chakra in a way that is felt by others, and which is in tune with the vibratory energies of the perfect universe. It can help remind the user of the reasons for being in the physical body and for living on the Earth plane. It is wonderful to wear or carry, giving one a feeling of being free, like being on top of a mountain with the breeze ruffling your hair. The insights are astonishing when meditating with sugilite.


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