Very Interesting Info About Azurite

Very Interesting Info About Azurite

 

Collectors prize deep blue azurite crystals, but faceted gems are extremely rare. However, azurite frequently occurs mixed with green malachite, and this material is commonly used for cabochons and decorative objects.

Azurite Information
Name
Azurite
Crystallography
Monoclinic. Crystals may be large and perfect, tabular, prismatic; also massive, earthy, banded, stalactitic.
Refractive Index
1.730-1.836
Colors
Light and dark azure blue.
Luster
Vitreous (crystals) to earthy or dull.
Hardness
3.5-4
Fracture
Conchoidal
Specific Gravity
3.77
Birefringence
0.110
Cleavage
Perfect 1 direction
Luminescence
None
Luminescence Present
No
Transparency
Transparent to opaque.
Absorption Spectrum
Line at 500.
Formula
Cu3 (CO3)2(OH)2
Pleochroism
Strong, in shades of blue.
Optics
α = 1.730; β = 1.758 γ = 1.836; Biaxial (+), 2V ~ 67°.
Optic Sign
Biaxial +

Etymology
In allusion to the color, derived from the Persian word lazhward, meaning blue.

Occurrence
Secondary mineral in copper deposits.

Comments
Azurite occurs in fine crystals in many localities. When it occurs in massive form, the material is almost always mixed with malachite, another copper carbonate mineral. Lapidaries cut this mixture, called azurite-malachite or azurmalachite, into very attractive cabochons and large decorative items, such as boxes.

Burnite is a mixture of azurite and cuprite (copper oxide).
Azurites, malachites, and cuprites are all idiochromatic; they receive their color from copper. However, copper creates different colors in these different species. Azurites are always blue, malachites are always green, and cuprites are always red. When they occur mixed, these minerals appear as bands and/or “eyes” of their distinctive colors.
Since azurite is more unstable than malachite, it often pseudomorphs into malachite. This means its chemistry changes to malachite while retaining azurite’s external crystal form.
Azurite’s distinctive, intense blue color makes it a popular collector’s stone. However, even small azurites are extremely dark, virtually black. Since azurites have such low hardness (3.5-4) and great sensitivity to heat, faceting them is also very challenging. This combination of factors makes faceted azurites very rare.

Identifying Characteristics
Artists have used blue pigments made from azurite since ancient times. Perhaps not surprisingly, people have confused this stone with lapis lazuli, another well-known historic source of blue pigments. Sodalite, another gem material commonly cabbed and carved, is sometimes confused with azurite as well.
Although these materials may show similar colors, azurites have a higher refractive index (RI) and specific gravity (SG) as well as a lower hardness. Azurites are also birefringent, while lapis and sodalite are not.

Synthetics
Scientists have synthesized azurites for geological research as well as research into pigments. Crystals have also been created in labs. However, due to azurite’s physical limitations, any such lab-created material would make an unlikely option for jewelry use.
Nevertheless, you can easily find “synthetic azurites” for sale online, especially in jewelry. Be aware that “reconstructed” azurmalachite — a compressed and stabilized, plastic-impregnated form of azurite and malachite — can be cabbed and has good color and toughness. This material has been available since 1989 at the latest, and by 1992, imitations of azurmalachite in jewelry were popular (if not always convincing). More recently, such materials have been found to contain artificial veins of copper.
Its possible vendors are selling this “reconstructed” material or other simulants as “synthetic.” In such cases, “synthetic” means imitation or “fake” in the popular sense. These stones aren’t identical optically and physically to the natural, mined material. Buyer beware.
Although natural azurite is a coveted collector’s stone, it’s still not very well-known to consumers. Thus, some vendors may misrepresent azurites as “copper lapis” or “Arctic opal,” perhaps to garner more sales interest by associating them with more popular gems. Of course, azurites aren’t lapis or opals but a distinct gem species.

Enhancements
Azurites generally receive no treatments or enhancements. (“Reconstructed” azurmalachite may receive pore-filling stabilization treatments similar to turquoise).

Sources
Notable gem-quality localities include the following:
United States: Morenci and Bisbee, Arizona: banded and massive material, also crystals; Kelly, New Mexico (also other localities in that state).
Chessy, France: the type locality, material sometimes called chessylite, fine crystals in large groups.
Eclipse Mine, Muldiva-Chillagoe area, Queensland, Australia: gemmy crystals up to about 9 grams.
Tsumeb, Namibia: fine, tabular crystals, some facetable in small bits.
Zacatecas, Mexico: fine but small crystals.
China; Democratic Republic of Congo; Greece; Italy; Laos; Morocco; Pakistan; Peru; Russia.

Stone Sizes
Facetable crystals are always tiny, and cut gems rarely weigh more than a carat. Larger stones would most likely be so dark as to be opaque. Gem cutters sometimes take dark blue crystalline material and create cabochons up to several inches across.

Care
In addition to its relatively low hardness and brittle tenacity, azurite will gradually lose its blue color when exposed to air, heat, and light. Thus, reserve these gems for occasional jewelry use with protective settings. Store them separately from harder jewelry stones, in darkness, and sealed to reduce contact with air.
Azurites are difficult to facet due to their low hardness, perfect cleavage, and heat sensitivity. Furthermore, their copper content makes their dust toxic. Accidental ingestion could lead to acute distress, like vomiting, and chronic exposure could lead to liver and kidney damage. Faceters should wear protective masks and, ideally, use a glovebox to prevent inhaling or ingesting azurite particles during cutting and polishing. Wearing or handling finished pieces should pose no hazards.
Clean these gems only with water, mild detergent, and a soft brush. Avoid any cleaner that contains acids.

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