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Malachite is a copper carbonate hydroxide mineral, with the formula Cu 2 CO 3 (OH) 2.This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fractures and deep, underground spaces, where the water table and hydrothermal fluids provide the means for chemical precipitation.
Both malachite and azurite, as well as synthetic basic copper carbonate have been used as pigments. [10] One example of the use of both azurite and its artificial form blue verditer [ 11 ] is the portrait of the family of Balthasar Gerbier by Peter Paul Rubens . [ 12 ]
Azurite and malachite on iron oxide gossan from Arizona, USA. (~5.0 centimeters across at its widest) Blue = azurite Green = malachite Reddish-brown = gossan matrix A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties.
The bulk of the products was well-crystallized malachite Cu 2 CO 3 (OH) 2, but a small yield of a rhombohedral substance was also obtained, claimed to be CuCO 3. [6] However, this synthesis was apparently not reproduced. [2] Reliable synthesis of true copper(II) carbonate was reported for the first time in 1973 by Hartmut Ehrhardt et al.
Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species. Within a mineral species there may be variation in physical properties or minor amounts of impurities that are recognized by mineralogists or wider society as a mineral variety.
Associated minerals are quartz, limonite, azurite, malachite, cuprite, and other secondary copper minerals. It is typically found as botryoidal or rounded masses and crusts, or vein fillings. A 2006 study has produced evidence that chrysocolla may be a microscopic mixture of the copper hydroxide mineral spertiniite , amorphous silica and water.
Physical properties applied for classification include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, cleavage and fracture, and specific gravity. Other less general tests include fluorescence , phosphorescence , magnetism , radioactivity , tenacity (response to mechanical induced changes of shape or form ...
The optical properties (color, intensity) of minerals such as azurite and malachite are characteristic of copper(II). Many coordination complexes of copper(II) exhibit similar colors. According to crystal field theory, the color results from low energy d-d transitions associated with the d 9 metal center. [12] [13]