Very Rare Azurite in Kaolinite display specimen from Malbunka Copper Mine N

Item Information

Dimensions (mm) 60 x 55 x 23mm
Weight (carats) 387.5 carats
No Treatment

Very Rare Azurite in Kaolinite display specimen from Malbunka Copper Mine Northern Territory, Australia

list price $500.00

Azurite is a soft, deep blue copper mineral produced by the oxidation weathering of copper ore deposits. It is a favorite amongst mineral collectors because of its rich blue color and wide availability in a variety of forms and color variations, from sharp, lustrous brilliant dark blue crystals to thick, rich, colorful royal blue coatings on matrix. Azurite suns are a unique form of azurite that have been found in only one place in the world: the Malbunka Copper Mine (formerly the Namatjira prospect) near Areyonga, beneath a hill in the desert in Northern Territory, Australia. Malbunka is the name of the Aboriginal clan that owns the land. MINERALOGY
Azurite suns form between layers of a clay mineral called kaolinite, with some sandstone rich lenses. The kaolinite is the matrix for the suns. The kaolinite is thought to be the result of the weathering of a tuffaceous volcanic rock. The azurite was formed by hydrothermal fluids carrying copper ions, which moved through bedding planes/slip planes in the kaolinite rock formation. Carbonate molecules and copper ions in the groundwater nucleated around mineral grains in the kaolinite, which resulted in crystallization of the azurite. Because the azurite was forced to grow in a laterally compressed, radiating manner along preferred bedding planes, the azurite grew uniformly outward, frequently producing near perfect circles. Azurite in clay matrix deposits normally forms spherical shapes (balls), such as those found at the Blue Grotto Mine, La Sal, Utah.

The Malbunka Mine is the only mine in the world that currently produces the discoidal blue suns. Both the azurite and kaolinite matrix are very stable. The genesis of the blue suns is said to parallel that of the flat pyrite discs from the coal mines in Illinois. Bedding plane distortion, two-dimensional triple point junctions where three suns have grown into each other, bedding plane control and distortional features in specimens due to volume changes in the tight enclosing rock, all provide evidence that the blue suns are post-sediment depositional concretions, not algal mat replacements. COLOR
The azurite suns vary in color from a light sky blue, through royal blue, to a dark, indigo blue. The color variations are related to the amount of clay that was caught up in the accreting azurite during the growth of the specimen. Light blue specimens contain more very fine white clay than darker blue specimens. Dark blue specimens can be seen distorting enclosing bedding instead of enveloping it. SPECIMEN PREPARATION
During mining, the suns are found enclosed in the kaolinite matrix. The matrix is later cleaned away from one side of the specimen, using fine water sprays set at the proper pressure and density to remove the softer clay without damaging the azurite, allowing the specimen to be cleaned down to the layer with the suns. (They should not be dipped in water, as this would make them tend to fall apart). The azurite suns are naturally lustrous, and do not need to be treated or glazed to make them glossy. According to the mine operator, they are not reattached or glued to the matrix; if detached during mining or cleaning, they stay off and become single azurite sun stock. The kaolin is a clay, and if untreated, it would leave chalky marks on your hands when you touch it. To prevent this, it is sprayed with non-gloss artists’ fixative to reduce kaolin loss. Once the kaolinite is removed from one side, the azurite suns are left sitting on the bone white kaolinite, which creates a very dramatic, natural contrast of blue on white.

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Auction ID 735639
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Starts 26th Feb 2018 8:24pm PST

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