USA ROCKS ARIZONA MALACHITE ROUGH POLISHED BOTRYOIDAL BAGDAD EUREKA MINE YAVAPAI

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USA ROCKS ARIZONA MALACHITE ROUGH POLISHED BOTRYOIDAL BAGDAD EUREKA MINE YAVAPAI
USA ROCKS ARIZONA MALACHITE ROUGH POLISHED BOTRYOIDAL BAGDAD EUREKA MINE YAVAPAI
USA ROCKS ARIZONA MALACHITE ROUGH POLISHED BOTRYOIDAL BAGDAD EUREKA MINE YAVAPAI
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Description
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(2) TWO PIECES
UNITED STATES MINED MALACHITE
FROM THE EUREKA MINES THE BAGDAD VEIN IN
YAVAPAI COUNTY ARIZONA
1.8oz BOTRYOIDAL SPECIMEN
COPPERS AND SILICATES
48mm X 45mm X 28mm
.6oz POLISHED STONE
31mm X 25mm X 12mm
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FYI
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Malachite is a copper carbonate hydroxide mineral, with the formula Cu2CO3(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. Individual crystals are rare, but occur as slender to acicular prisms. Pseudomorphs after more tabular or blocky azurite crystals also occur.
The stone's name derives (via Latin: molochītis, Middle French: melochite, and Middle English melochites) from Greek Μολοχίτης λίθος molochites lithos, "mallow-green stone", from μολόχη molochē, variant of μαλάχη malāchē, "mallow". The mineral was given this name due to its resemblance to the leaves of the mallow plant.
Malachite was extensively mined at the Great Orme Mines in Britain 3,800 years ago, using stone and bone tools. Archaeological evidence indicates that mining activity ended c. 600 BCE, with up to 1,760 tonnes of copper being produced from the mined malachite.
Archaeological evidence indicates that the mineral has been mined and smelted to obtain copper at Timna Valley in Israel for more than 3,000 years. Since then, malachite has been used as both an ornamental stone and as a gemstone.
Occurrence
Malachite often results from the supergene weathering and oxidation of primary sulfidic copper ores, and is often found with azurite (Cu3(CO3)2(OH)2), goethite, and calcite. Except for its vibrant green color, the properties of malachite are similar to those of azurite and aggregates of the two minerals occur frequently. Malachite is more common than azurite and is typically associated with copper deposits around limestones, the source of the carbonate.
Large quantities of malachite have been mined in the Urals, Russia. Ural malachite is not being mined at present, but G.N Vertushkova reports the possible discovery of new deposits of malachite in the Urals. It is found worldwide including in the Democratic Republic of the Congo; Gabon; Zambia; Tsumeb, Namibia; Mexico; Broken Hill, New South Wales; Burra, South Australia; Lyon, France; Timna Valley, Israel; and the Southwestern United States, most notably in Arizona.
Malachite was used as a mineral pigment in green paints from antiquity until c. 1800. The pigment is moderately lightfast, sensitive to acids, and varying in color. This natural form of green pigment has been replaced by its synthetic form, verditer, among other synthetic greens.
Malachite is also used for decorative purposes, such as in the Malachite Room in the Hermitage Museum, which features a huge malachite vase, and the Malachite Room in Castillo de Chapultepec in Mexico City. Another example is the Demidov Vase, part of the former Demidov family collection, and now in the Metropolitan Museum of Art. "The Tazza", a large malachite vase, one of the largest pieces of malachite in North America and a gift from Tsar Nicholas II, stands as the focal point in the centre of the room of Linda Hall Library. In the time of Tsar Nicolas I decorative pieces with malachite were among the most popular diplomatic gifts.
Symbolism and superstitions
A 17th-century Spanish superstition held that having a child wear a lozenge of malachite would help them sleep, and keep evil spirits at bay. Marbodus recommended malachite as a talisman for young people because of its protective qualities and its ability to help with sleep. It has also historically been worn for protection from lightning and contagious diseases and for health, success, and constancy in the affections. During the Middle Ages it was customary to wear it engraved with a figure or symbol of the Sun to maintain health and to avert depression to which Capricorns were considered vulnerable.
In ancient Egypt the colour green (wadj) was associated with death and the power of resurrection as well as new life and fertility. Ancient Egyptians believed that the afterlife contained an eternal paradise, referred to as the "Field of Malachite", which resembled their lives but with no pain or suffering.
Ore uses
Simple methods of copper ore extraction from malachite involved thermodynamic processes such as smelting. This reaction involves the addition of heat and a carbon, causing the carbonate to decompose leaving copper oxide and an additional carbon source such as coal converts the copper oxide into copper ore.
The basic word equation for this reaction is:
Copper carbonate + heat --> carbon dioxide + copper oxide (color changes from green to black).
Copper oxide + carbon --> carbon dioxide + copper (color change from black to copper colored).
Malachite is a low grade copper ore, however, due to increase demand for metals, more economic processing such as hydrometallurgical methods (using aqueous solutions such as sulfuric acid) are being used as malachite is readily soluble in dilute acids. Sulfuric acid is the most common leaching agent for copper oxide ores like malachite and eliminates the need for smelting processes.
The chemical equation for sulfuric acid leaching of copper ore from malachite is as follows: Cu2(OH)2CO3 + 2H2SO4 --> 2CuSO4 + CO2 +3H2O.
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A lapidary (the word means "concerned with stones") is an artisan who practices the craft of working, forming and finishing stone, mineral, gemstones, and other suitably durable materials (amber, shell, jet, pearl, copal, coral, horn and bone, glass and other synthetics) into functional and/or decorative, even wearable, items (e.g. cameos, cabochons, and more complex facetted designs). The adjectival term is also extended to refer to such arts. Diamond cutters are generally not referred to as lapidaries, due to their highly specialized techniques which are required to work diamond successfully.
The arts of a sculptor or stonemason are generally too broad in scale to fall within the definition, though chiseling inscriptions in stone, and preparing laboratory 'thin sections' may be considered lapidary arts. The term is most commonly associated with jewelry and decorative household items (e.g. bookends, clock faces, ornaments, etc.) A specialized form of lapidary work is the inlaying of marble and gemstones into a marble matrix, known in English as "pietra dura" for the hard stones like onyx, jasper and carnelian that are used, but called in Florence and Naples, where the technique was developed in the 16th century, opere di commessi. The Medici Chapel at San Lorenzo in Florence is completely veneered with inlaid hard stones. A lapidary specialty developed from the late 18th century in Naples and Rome are the "micro-mosaics" assembled out of many minute slivers of stone to create still life, cityscape views and the like.
In China, lapidary work specializing in jade carving has been continuous since the Shang dynasty.
There exist three broad categories of lapidary arts. These are the procedures of tumbling, cabochon cutting, and faceting. The distinction is somewhat loose, and leaves a broad range within the term cabochon.
At present most lapidary work is accomplished using motorized equipment and resin or metal bonded diamond tooling in successively decreasing particle sizes until a polish is achieved. Often, the final polish will use a different medium, such as tin oxide, glasitite or cerium(IV) oxide. Older techniques, still popular with hobbyists, used bonded grinding wheels of silicon carbide, with only using a diamond tipped saw. Diamond cutting, because of the extreme hardness of diamonds, cannot be done with silicon carbide, and requires the use of diamond tools.
There are also many other forms of lapidary, not just cutting and polishing stones and gemstones. These include; casting, faceting, carving, jewelery, mosaics (eg. little slices of opal on potch, obsidian or another black stone and with a clear dome (glass or crystal quartz) on top. There are lapidary clubs through-out the world and in Australia there is an annual gemshow, the Gemborree which is a nation-wide lapidary competition. The largest mineral show in the world is the Tucson Gem and Mineral Society Show held annually in Arizona, USA.
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