Chrysocolla

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Chrysocolla
Chrysocolla-230109.jpg
Chrysocolla, Ray Mine, Scott Mountain area, Mineral Creek District, Pinal County, Arizona, USA
General
Category Phyllosilicate mineral mineraloid
Formula
(repeating unit)
Cu
2–x
Al
x
{H
2–x
Si
2
O
5
)(OH)
4
•nH
2
O
 (x<1) [1]
Strunz classification 9.ED.20
Crystal system Orthorhombic
Unknown space group
Unit cell a = 5.7 Å, b = 8.9 Å,
c = 6.7 Å; Z = 1
Identification
ColorBlue, cyan or blue-green, green, blackish blue to black, or brown and rarely yellow
Crystal habit Massive, nodular, botryoidal
Cleavage none
Fracture Irregular/uneven, sub-conchoidal
Tenacity Brittle to sectile
Mohs scale hardness2.5 - 3.5 ( or 7 - chrysocolla chalcedony, high silica content )
Luster Vitreous to dull
Streak white to a blue-green color
Diaphaneity Translucent to opaque
Specific gravity 1.9 - 2.4
Optical propertiesBiaxial (-)
Refractive index nα = 1.575 - 1.585 nβ = 1.597 nγ = 1.598 - 1.635
Birefringence δ = 0.023 - 0.050
References [2] [3] [1] [4]

Chrysocolla is a hydrated copper phyllosilicate mineral and mineraloid with formula Cu
2–x
Al
x
{H
2–x
Si
2
O
5
)(OH)
4
•nH
2
O
(x<1) [1] or (Cu,Al)
2
H
2
Si
2
O
5
(OH)
4
•nH
2
O)
. [3]

Contents

The structure of the mineral has been questioned, as a 2006 spectrographic study suggest material identified as chrysocolla may be a mixture of the copper hydroxide spertiniite and chalcedony. [5]

History

The name comes from the ancient Greek χρυσός (chrysos) and κολλα (kolla), "gold" and "glue," [6] in allusion to the name of the material used to solder gold and was first used by Theophrastus in 315 BC.

Geology

Chrysocolla has a cyan (blue-green) color and is a minor ore of copper, having a hardness of 2.5 to 7.0. It is of secondary origin and forms in the oxidation zones of copper ore bodies. 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. [5] [1]

Jewelry

Due to being somewhat more common than turquoise, its wide availability, and vivid, beautiful blue and blue-green colors, chrysocolla has been popular for use as a gemstone for carvings and ornamental use since antiquity. It is often used in silversmithing and goldsmithing in place of turquoise and is relatively easy to work and shape. Chrysocolla exhibits a wide range of Mohs hardness ranging from 2 through 7, which is dependent on the amount of silica incorporated into the stone when it is forming. Generally, dark navy blue chrysocolla is too soft to be used in jewelry, while cyan, green, and blue-green chrysocolla can have a hardness approaching 6, similar to turquoise. Chrysocolla chalcedony is a heavily silicified form of chrysocolla that forms in quartz deposits and can be very hard and approach a hardness of 7. [7] [8] [9]

See also

Related Research Articles

Quartz Mineral made of silicon and oxygen.

Quartz is a hard, crystalline mineral composed of silicon and oxygen atoms. The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar.

Chalcedony Microcrystalline varieties of silica, may contain moganite as well

Chalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Chalcedony's standard chemical structure (based on the chemical structure of quartz) is SiO2 (silicon dioxide).

Turquoise Opaque, blue-to-green mineral: hydrous phosphate of copper and aluminium

Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminium, with the chemical formula CuAl6(PO4)4(OH)8·4H2O. It is rare and valuable in finer grades and has been prized as a gemstone and ornamental stone for thousands of years owing to its unique hue. Like most other opaque gems, turquoise has been devalued by the introduction onto the market of treatments, imitations and synthetics.

Chalcopyrite Copper iron sulfide mineral

Chalcopyrite ( KAL-ko-PY-ryt) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green tinged black.

Azurite Copper carbonate mineral

Azurite is a soft, deep-blue copper mineral produced by weathering of copper ore deposits. During the early 19th century, it was also known as chessylite, after the type locality at Chessy-les-Mines near Lyon, France. The mineral, a basic carbonate with the chemical formula Cu3(CO3)2(OH)2, has been known since ancient times, and was mentioned in Pliny the Elder's Natural History under the Greek name kuanos (κυανός: "deep blue," root of English cyan) and the Latin name caeruleum. Since antiquity, azurite's exceptionally deep and clear blue has been associated with low-humidity desert and winter skies. The modern English name of the mineral reflects this association, since both azurite and azure are derived via Arabic from the Persian lazhward (لاژورد), an area known for its deposits of another deep-blue stone, lapis lazuli ("stone of azure").

Cuprite

Cuprite is an oxide mineral composed of copper(I) oxide Cu2O, and is a minor ore of copper.

Dioptase

Dioptase is an intense emerald-green to bluish-green copper cyclosilicate mineral. It is transparent to translucent. Its luster is vitreous to sub-adamantine. Its formula is Cu6Si6O18·6H2O (also reported as CuSiO2(OH)2). It has a hardness of 5, the same as tooth enamel. Its specific gravity is 3.28–3.35, and it has two perfect and one very good cleavage directions. Additionally, dioptase is very fragile, and specimens must be handled with great care. It is a trigonal mineral, forming 6-sided crystals that are terminated by rhombohedra.

Turquoise is a blue/green color, based on the gem of the same name. The word turquoise comes from the French for "Turkish", as the gem was originally imported from Turkey. The first recorded use of turquoise as a color name in English was in 1573.

Chrysoprase

Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony that contains small quantities of nickel. Its color is normally apple-green, but varies to deep green. The darker varieties of chrysoprase are also referred to as prase.

Copper(II) hydroxide Hydroxide of copper

Copper(II) hydroxide is the hydroxide of copper with the chemical formula of Cu(OH)2. It is a pale greenish blue or bluish green solid. Some forms of copper(II) hydroxide are sold as "stabilized" copper(II) hydroxide, although they likely consist of a mixture of copper(II) carbonate and hydroxide. Cupric hydroxide is a strong base, although its low solubility in water makes this hard to observe directly.

Egyptian blue Pigment used in ancient Egypt

Egyptian blue, also known as calcium copper silicate (CaCuSi4O10 or CaOCuO(SiO2)4 (calcium copper tetrasilicate)) or cuprorivaite, is a pigment that was used in ancient Egypt for thousands of years. It is considered to be the first synthetic pigment. It was known to the Romans by the name caeruleum. After the Roman era, Egyptian blue fell from use and, thereafter, the manner of its creation was forgotten. In modern times, scientists have been able to analyze its chemistry and reconstruct how to make it. However, Raphael apparently also rediscovered it and used it in his Triumph of Galatea.

Howlite

Howlite, a calcium borosilicate hydroxide (Ca2B5SiO9(OH)5), is a borate mineral found in evaporite deposits.

Plancheite

Plancheite is a hydrated copper silicate mineral with the formula Cu8Si8O22(OH)4•(H2O). It is closely related to shattuckite in structure and appearance, and the two minerals are often confused.

Spertiniite

Spertiniite is a rare copper hydroxide mineral. Chemically it is copper(II) hydroxide with formula Cu(OH)2. It occurs as blue to blue green tabular orthorhombic crystal aggregates in a secondary alkaline environment altering chalcosite. Associated minerals include chalcocite, atacamite, native copper, diopside, grossular and vesuvianite.

Mohawkite

Mohawkite is a rare rock consisting of mixtures of arsenic, silver, nickel, skutterudite and copper, with the formula Cu3As up to Cu6As, and the most desirable material was usually found in white quartz matrix. It has a hardness of 3-3.5 and a metallic luster. It is named after the Mohawk mine where it was originally found. Colors range from brassy-yellow to metallic gray, and sometimes will have a blue or greenish surface tarnish. These colors come from its two main ingredients, the arsenic-rich copper minerals algodonite and domeykite. Its color may resemble pyrrhotite, but unlike pyrrhotite, mohawkite is not magnetic.

Mottramite

Mottramite is an orthorhombic anhydrous vanadate hydroxide mineral, PbCu(VO4)(OH), at the copper end of the descloizite subgroup. It was formerly called cuprodescloizite or psittacinite (this mineral characterized in 1868 by Frederick Augustus Genth). Duhamelite is a calcium- and bismuth-bearing variety of mottramite, typically with acicular habit.

Chrysocolla, also known as "goldsmith's solder" and "solder of Macedonia" (Pseudo-Democritus), denotes:

Copper silicate may refer to any silicate of copper generally; more specifically:

Lemanskiite is a mineral that was first discovered in a mine at Abundancia mine, El Guanaco mining district, Chile, with the ideal formula of NaCaCu5(AsO4)4Cl•3H2O. Originally, this mineral was discovered as being dimorphus with lavendulan, but in 2018 it was revised to only have 3 water molecules. Lemanskiite typically occurs as rosette-shaped aggregates of thin lamellar or needle-shaped aggregates, such as lammerite. Lemanskiite is dark sky blue with a light blue streak, it is brittle with an excellent cleavage plane. It was found on a dumping site in the abandoned Abundancia mine, El Guanaco mining district, Region II, Antofagasta Province, Chile The new mineral has been named after Chester S. Lemanski, Jr. This mineral and name were then approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association.

References

  1. 1 2 3 4 "Chrysocolla: Chrysocolla mineral information and data". www.mindat.org.
  2. "Mineralienatlas - Fossilienatlas".
  3. 1 2 "Handbook of Mineralogy" (PDF).
  4. Barthelmy, Dave. "Chrysocolla Mineral Data". webmineral.com.
  5. 1 2 François Farges, Karim Benzerara, Gordon E. Brown, Jr.; Chrysocolla Redefined as Spertiniite; SLAC-PUB-12232; 13th International Conference On X-Ray Absorption Fine Structure (XAFS13); July 9-14, 2006; Stanford, California
  6. Spencer, Leonard James (1911). "Chrysocolla"  . In Chisholm, Hugh (ed.). Encyclopædia Britannica . 6 (11th ed.). Cambridge University Press. p. 320.
  7. "Gem Silica: The blue, most valuable variety of chalcedony". geology.com.
  8. "Chrysocolla: The gemstone chrysocolla information and pictures". www.minerals.net.
  9. "Chrysocolla Value, Price, and Jewelry Information - IGS".