Azurite Suns: Mineral Masterpieces from Australia

Write By: tmmadmin Published In: Mineral Species Created Date: 2014-11-30 Hits: 7054 Comment: 0


2.8" azurite sun on kaolinite

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. Other minerals found include minor malachite, chrysocolla, and atacamite, but not in specimen quality.


2.8" azurite sun on kaolinite

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.


4" kaolinite matrix with 5 azurite suns to 1.8"

MINE LOCATION AND HISTORY
The Malbunka Copper Mine is located in the Gardiner Range in the Northern Territory about 220 km W of Alice Springs, near the villages of Areyonga and Utju. The desert has a rocky terrain with small hills. The Tanami was the Northern Territory's final frontier and was not fully explored until well into the twentieth century. Until 2005, the mine was called the "Namajtira prospect". It was mined for azurite suns as far back as 1976, which was the last time these amazing specimens were seen. The name Namajtira was changed by the Western Aranda Malbunka clan and their relevant djungaiyi/kurtungkula (i.e. "managers") in 2005. The Malbunka land owning clan was never consulted by the initial miners or government when the name was first assigned to the site. Under Aboriginal law, no person has the right to impose a clan name from a separate clan area over other clan areas; hence respect for Aboriginal law via the name change was fundamental to commencing the mineral specimen mining project.


Map showing the location of the Malbunka Copper Mine

The Malbunka Copper Mine (MCM) is operated via an agreement under the Aboriginal Land Rights (Northern Territory) Act 1976 by Dehne McLaughlin. A land rental and unprecedented royalty is paid to the land owners and an annual administration fee to the Central Land Council. Exploration and mining occurs underground. An underground decline has delineated high quality specimens including crystalline lustrous blue azurite nodules, as well as the more typical azurite "suns" for which this location is noted.

The first azurite suns from the Malbunka Copper Mine appeared at the Tucson Gem, Rock and Mineral Show in 2009. Mine owner Dehne McLaughlin brought his own stock to sell for the first time in 2010. An article is scheduled to be published late in 2012 in Rocks and Minerals magazine with more information about this exciting material. Research is underway to determine the genesis of the azurite.


3" azurite sun on kaolinite

SITE PHOTOS
Many thanks to Dehne McLaughlin for much of the information above, and for the site photos below.


Blue seams of azurite in situ. Extracting and cleaning these specimens is a time intensive process.



Azurite suns in situ (note marks made by electric chisels used to extract specimens)

 


The sampling decline, showing faulting


Azurite suns in cross section adjacent to a fracture showing hydrothermal alteration (bleaching)in the decline working face.


View of the mine taken from a nearby hill showing terrain


Azurite suns and balls from the Malbunka Copper Mine at Dehne McLaughlin's stall at the Broken Hill Gem and Mineral Show, 2011 (for scale, name cards are 5cm across)

All specimens and specimen photos courtesy of www.TreasureMountainMining.com, except as noted.

To see our current selection of azurite specimens, including azurite suns, please click here.

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