It is often found associated with and altering too malachite, but is considerable less common than this mineral. Other commonly associated minerals include chalcocite, chalcopyrite, cuprite, tenorite, calcite, and goethite.
Most of the azurite occurrences in Wisconsin are from the more copper-rich deposits associated with the zinc-lead ares in southwestern Wisconsin, notable Iowa and Crawford Counties. Sterling Heyl et al. Hobbs described the crystals in some detail, noting that they may be 4 mm. The crystals have complex tabular habit, a deep blue color, and, occasionally, thin coatings of malachite. The azurite occurs with tenorite and limonite as alteration products of chalcopyrite. Blue to very dark blue.
Light blue. Crystal System. Crystal Forms and Aggregates. Usually in small crystals, which are in prismatic , tabular , or equidimensional form.
Crystals are sometime striated. Other forms are massive , crusty , radiating , fibrous , earthy , columnar , stalactitic , as thin needles, and in ball-like aggregates. Also occurs in dense groups of tabular or prismatic crystals.
Azurite may also form as a pseudomorph over other minerals, retaining the original crystal shape of the mineral that it formed a pseudomorph over. Rarely translucent on thin edges. Specific Gravity. Vitreous or dull. Conchoidal or splintery. Other ID Marks. Complex Tests. Effervesce s in hydrochloric acid and soluble in ammonia.
In Group. Striking Features. Deep blue color, blue streak, and common association with green Malachite. As a secondary mineral in the oxidation zone of copper deposits. Rock Type. Sedimentary , Metamorphic. Popularity It is a white granite with orbs of bright blue azurite dispersed through the stone. Most people who see it initially think that it is fake, but it can be sawn to reveal round azurite areas inside, and x-ray diffraction reveals azurite. This azurite granite is commonly called "K2 granite" after the second-highest mountain in the world, because the rock was first discovered near the base of the mountain.
Azurite Pigment: High-purity azurite finely ground into a powder and ready for use as a pigment. Azurite has been used as a pigment for thousands of years. Today, synthetic pigments are used more than natural pigments.
They are lower in cost and standardized in their properties. Azurite was ground and used as a pigment in blue paint as early as ancient Egypt. Through time, its use became much more common. During the Middle Ages and Renaissance, it was the most important blue pigment used in Europe. Much of the azurite used to make the pigment was mined in France. Making pigment from azurite was costly. During the Middle Ages it was difficult to mine, transportation was slow, and grinding and processing were slow and difficult.
Azurite pigment was gradually replaced, starting in the 18th century, when man-made pigments such as "Prussian blue" and "blue verditer" were invented. These synthetic pigments are standardized products with uniform properties. That makes them predictable in their use. They are also less costly to produce.
Many paintings done during the Middle Ages, before azurite was replaced with Prussian blue, show deterioration of the blue color. Over time and exposure to the atmosphere and light, azurite slowly weathers to malachite. Much of the blue azurite pigment used during the Middle Ages now shows obvious signs of green malachite as a weathering product. This is another reason why man-made pigments are now used instead of azurite. Azurite pigment and paints are still available today and are easy to find.
But they are mainly used by painters who want to employ historical methods in their work. Azurite Crystals: Well-formed crystals of azurite are popular with mineral collectors because of their rarity and beauty. This small cluster of blade-shaped azurite crystals is from the Tsumeb Mine in Namibia. This specimen is small, about 1. Azurite is popular with mineral collectors. They appreciate its deep blue monoclinic crystals, nodular habit with interesting structures, and representative examples of its botryoidal and stalactitic habits.
Excellent specimens can sell for hundreds, thousands, or tens of thousands of dollars depending upon their quality and size. The instability of azurite is a problem for collectors. If exposed to heat or high humidity, specimen surfaces will begin to weather to malachite. This causes a dull, faded or greenish appearance depending upon the severity of alteration. Valuable specimens are best stored in closed collection drawers where there is limited air circulation, darkness, and cool, stable temperatures.
Home » Minerals » Azurite Azurite A deep blue mineral, gem material, ornamental stone, ore of copper, and pigment. Article by: Hobart M. Chemical Composition Copper carbonate. Find Other Topics on Geology. Maps Volcanoes World Maps.
Deep blue color, effervescence in dilute HCl, high specific gravity, low hardness. Copper carbonate. Minor ore of copper, gem material, ornamental stone, pigment. Rock and Mineral Kits. Are Water and Ice Minerals? Mohs Hardness Scale.
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