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Chatoyancy
 
 
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In gemology
Gemology

Gemology or gemmology is the science, art and profession of identifying and evaluating gemstones. It is considered a geoscience and a branch of mineralogy....
, chatoyancy (), or chatoyance, is an optical
Optics

Optics is the study of the behavior and properties of light including its optical phenomena with matter and its imaging by optical instruments....
 reflectance effect seen in certain gemstone
Gemstone

A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which — when cut and polished — is used to make jewellery or other adornments....
s. Coined from the French "oeil de chat", meaning "cat's eye", chatoyancy arises either from the fibrous structure of a material, as in tiger eye quartz
Quartz

Quartz is the most abundant mineral in the Earth's continental crust . It is made up of a Crystal structure of silica tetrahedra. Quartz has a hardness of 7 on the Mohs scale and a density of 2.65 g/cm?....
, or from fibrous inclusions or cavities within the stone, as in cat's eye chrysoberyl
Chrysoberyl

The mineral or gemstone chrysoberyl, not to be confused with beryl, is an aluminium of beryllium with the formula BeAl2O4....
.






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Tigers Eye
In gemology
Gemology

Gemology or gemmology is the science, art and profession of identifying and evaluating gemstones. It is considered a geoscience and a branch of mineralogy....
, chatoyancy (), or chatoyance, is an optical
Optics

Optics is the study of the behavior and properties of light including its optical phenomena with matter and its imaging by optical instruments....
 reflectance effect seen in certain gemstone
Gemstone

A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which — when cut and polished — is used to make jewellery or other adornments....
s. Coined from the French "oeil de chat", meaning "cat's eye", chatoyancy arises either from the fibrous structure of a material, as in tiger eye quartz
Quartz

Quartz is the most abundant mineral in the Earth's continental crust . It is made up of a Crystal structure of silica tetrahedra. Quartz has a hardness of 7 on the Mohs scale and a density of 2.65 g/cm?....
, or from fibrous inclusions or cavities within the stone, as in cat's eye chrysoberyl
Chrysoberyl

The mineral or gemstone chrysoberyl, not to be confused with beryl, is an aluminium of beryllium with the formula BeAl2O4....
. The effect can be likened to the sheen off a spool of silk: the luminous streak of reflected light is always perpendicular to the direction of the fibres. For a gemstone to show this effect best it must be cut en cabochon
Cabochon

A cabochon or cabachon, from the Middle French caboche , is a gemstone which has been shaped and polished as opposed to facetted. The resulting form is usually a convex top with a flat bottom....
, with the fibers or fibrous structures parallel to the base of the finished stone. Faceted stones are less likely to show the effect well.

Gem species known for this phenomenon include the aforementioned quartz
Quartz

Quartz is the most abundant mineral in the Earth's continental crust . It is made up of a Crystal structure of silica tetrahedra. Quartz has a hardness of 7 on the Mohs scale and a density of 2.65 g/cm?....
, chrysoberyl
Chrysoberyl

The mineral or gemstone chrysoberyl, not to be confused with beryl, is an aluminium of beryllium with the formula BeAl2O4....
, beryl
Beryl

The mineral beryl is a beryllium aluminium Silicate minerals#Cyclosilicates with the chemical formula Be3Al26. The hexagonal crystals of beryl may be very small or range to several meters in size....
 (especially var. aquamarine
Aquamarine

Aquamarine is a gemstone-quality transparent variety of beryl, having a delicate blue or turquoise color, suggestive of the tint of seawater. It is closely related to the gem emerald....
), tourmaline
Tourmaline

Tourmaline is a crystal silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classed as a semi-precious stone and the gem comes in a wide variety of colors....
, apatite
Apatite

Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, and chlorapatite, named for high concentrations of Hydroxyl−, Fluorine−, or Chlorine− ions, respectively, in the crystal....
, moonstone
Moonstone (gemstone)

Moonstone is typically a potassium aluminium Silicate minerals, with the chemical formula KAlSi3O8.The most common moonstone is of the mineral adularia....
 and scapolite
Scapolite

Scapolite , is a group of rock-forming silicate minerals composed of aluminium, calcium and sodium silicate with chlorine, carbonate and sulfate....
. Glass optical cable can also display chatoyancy if properly cut, and has become a popular decorative material in a variety of vivid colors.

Chatoyancy can also be used to refer to a similar effect in woodworking
Woodworking

Woodworking is the process of building, making or carving something using wood....
, where certain finishes will cause the wood grain
Wood grain

In speaking of wood the term grain is used, in several ways. Perhaps most important is that in woodworking techniques . In describing the application of a woodworking technique to a given piece of wood, the direction of the technique may be:...
 to achieve a striking three-dimensional appearance.

See also

  • Asterism (gemmology)
    Asterism (gemmology)

    In gemmology, an asterism is an optical phenomenon displayed by some ruby, sapphires, and other gemstone of an enhanced reflective area in the shape of a "star" on the surface of a cabochon cut from the stone....
  • Optical phenomenon
    Optical phenomenon

    An optical phenomenon is any observable event which results from the interaction of light and matter. See also list of optical topics and optics....


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