Lustre (or luster) is a description of the way light interacts with the surface of a crystal, rock, or mineral. In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific For example, a diamond is said to have an adamantine lustre and pyrite is said to have a metallic lustre. In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in The term is also used to describe other items with a particular sheen (for example, fabric, especially silk and satin, or metals). A textile is a flexible material comprised of a network of natural or artificial Fibres often referred to as thread or Yarn. Silk is a natural Protein Fiber, some forms of which can be woven into Textiles The best-known type of silk is obtained from cocoons Satin is a Cloth that typically has a glossy surface and a dull back The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across
The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome.
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Terminology
A broad range of terms are used to describe the lustre of minerals. It should be noted that lustre varies over a wide continuum, and so there are no rigid boundaries between the different terms. (For this reason, different sources can often describe the same mineral differently. ) The terms are frequently combined to describe intermediate types of lustre (for example, a "vitreous greasy" lustre).
Adamantine lustre
Adamantine minerals possess a superlative lustre, which is most notably seen in diamond. In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in Such minerals are transparent or translucent, and have a high refractive index (of 1. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium 9 or more). [1] Minerals with a true adamantine lustre are uncommon, with other examples being cerussite and zircon. Cerussite (also known as lead carbonate or White lead ore) is a Mineral consisting of Lead Carbonate (PbCO3 Zircon is a Mineral belonging to the group of nesosilicates. Its chemical name is Zirconium silicate and its corresponding chemical formula is
Minerals with a lesser (but still relatively high) degree of lustre are referred to as subadamantine, with examples including sapphire and garnet. Sapphire (antique greek hyacinthos refers to gem varieties of the mineral Corundum, an Aluminium oxide (Al2O3 when it is a color other than The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives
Dull lustre
Dull (or earthy) minerals exhibit little to no lustre, due to coarse granulations which scatter light in all directions, approximating a Lambertian reflector. Kaolinite is a Clay mineral with the chemical composition Al 2 Si 2 O 5( OH)4 See also Lambert's cosine law If a surface exhibits Lambertian reflectance, light falling on it is scattered such that the apparent brightness of the surface to an observer Examples include kaolinite and pyrolusite. Kaolinite is a Clay mineral with the chemical composition Al 2 Si 2 O 5( OH)4 Pyrolusite is a Mineral consisting essentially of Manganese dioxide ( Mn[[oxygen O]]2 and is important as an Ore of manganese A distinction is sometimes drawn between dull minerals and earthy minerals,[2] with the latter being coarser, and having even less lustre.
Greasy lustre
Greasy minerals resemble fat or grease. OPAL ( Open Pool Australian Lightwater reactor) is a 20 megawatt pool-type nuclear research reactor that was officially opened in April 2007 A greasy lustre is often caused by a great abundance of microscopic inclusions within the mineral. [1] Examples include opal and cordierite. OPAL ( Open Pool Australian Lightwater reactor) is a 20 megawatt pool-type nuclear research reactor that was officially opened in April 2007 Cordierite ( Mineralogy) or iolite ( Gemology) is a Magnesium Iron Aluminium cyclosilicate. Minerals with a greasy lustre many also feel greasy.
Metallic lustre
Metallic (or splendent) minerals have the lustre of polished metal, and in the ideal case will act as a mirror. A mirror is an object with a surface that has good Specular reflection; that is it is smooth enough to form an Image. Examples include galena, pyrite and magnetite. Galena is the natural mineral form of Lead sulfide. It is the most important Lead Ore mineral Magnetite is not to be confused with Magnesite or Maghemite. Magnetite is a ferrimagnetic Mineral with chemical
Pearly lustre
Pearly minerals consist of thin transparent co-planar sheets. Muscovite (also known as Common Mica, Isinglass, or Potash mica) is a phyllosilicate Mineral of Aluminium Light reflecting from these layers give them a lustre reminiscent of pearls. A pearl is a hard roundish object produced within the soft tissue (specifically the mantle) of a living shelled Mollusk. [3] Such minerals possess perfect cleavage,[1] with examples including muscovite and stilbite. Cleavage, in Mineralogy, is the tendency of crystalline materials to split along definite planes creating smooth surfaces of which there are several named types Muscovite (also known as Common Mica, Isinglass, or Potash mica) is a phyllosilicate Mineral of Aluminium Stilbite is a tectosilicate Mineral of the Zeolite group consisting of hydrated Calcium Aluminium Silicate, Na[[calcium
Resinous lustre
Resinous minerals have the appearance of resin, chewing gum or (smooth surfaced) plastic. Amber is Fossil tree Resin, which is appreciated for its color and beauty Resin, not to be confused with Rosin, is a Hydrocarbon Secretion of many Plants particularly coniferous trees. For songs called "Chewing Gum" see Chewing Gum (song Chewing gum is a type of Confectionery traditionally made of Chicle A principal example is amber, which is a form of fossilled resin. Amber is Fossil tree Resin, which is appreciated for its color and beauty
Silky lustre
Silky minerals have a parellel arrangement of extremely fine fibres,[1] giving them a lustre reminiscent of silk. This article is about the Mineral: for other meanings see Selenite (disambiguation. Gypsum is a very soft Mineral composed of Calcium sulfate dihydrate with the Chemical formula Ca[[sulfur S]] O 4·2 Silk is a natural Protein Fiber, some forms of which can be woven into Textiles The best-known type of silk is obtained from cocoons Examples include asbestos, ulexite and the satin spar variety of gypsum. Asbestos is a group of Minerals with long thin fibrous Crystals The word "asbestos" (῾ἀσβεστος is derived from a Greek adjective Ulexite ( Na[[calcium Ca]] B 5 O 9·8 H2O) (hydrated sodium calcium borate hydroxide is a Mineral This article is about the Mineral: for other meanings see Selenite (disambiguation. Gypsum is a very soft Mineral composed of Calcium sulfate dihydrate with the Chemical formula Ca[[sulfur S]] O 4·2 A fibrous lustre is similar, but has a coarser texture.
Submetallic lustre
Submetallic minerals have similar lustre to metal, but are duller and less reflective. Sphalerite (( Zn, Fe) S) is a Mineral that is the chief Ore of Zinc. A submetallic lustre often occurs in near-opaque minerals with very high refractive indices,[1] such as sphalerite, cinnabar and cuprite. Sphalerite (( Zn, Fe) S) is a Mineral that is the chief Ore of Zinc. Cinnabar, sometimes written cinnabarite, is a name applied to red Mercury(II sulfide ( Hg[[sulfide S]] or native Vermilion, the common Cuprite is a Mineral composed of Copper(I oxide Cu2O and is a minor Ore of copper
Vitreous lustre
Vitreous minerals have the lustre of glass. Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many This type of lustre is one of the most commonly seen,[3] and occurs in transparent or translucent minerals with relatively low refractive indices. [1] Common examples include calcite, quartz and fluorite. Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Fluorite (also called fluorspar) is a Mineral composed of Calcium fluoride, Ca[[Fluorine F2]]
Waxy lustre
Waxy minerals have a lustre resembling wax. Jade is an Ornamental stone. The term jade is applied to two different rocks that are made up of different Silicate minerals. Wax has traditionally referred to a substance that is secreted by Bees ( Beeswax) and used by them in constructing their Examples include jade and chalcedony. Jade is an Ornamental stone. The term jade is applied to two different rocks that are made up of different Silicate minerals. Chalcedony is a Cryptocrystalline form of Silica, composed of very fine intergrowths of the minerals Quartz and Moganite.
Optical phenomena
Asterism
Asterism is the display of a star-shaped luminous area. Sapphire (antique greek hyacinthos refers to gem varieties of the mineral Corundum, an Aluminium oxide (Al2O3 when it is a color other than In Gemmology, an asterism is an Optical phenomenon displayed by some rubies, Sapphires and other gems (i It is seen in some sapphires and rubies, where it is caused by impurities of rutile. Sapphire (antique greek hyacinthos refers to gem varieties of the mineral Corundum, an Aluminium oxide (Al2O3 when it is a color other than A Ruby is a pink to blood-red Gemstone, a variety of the Mineral Corundum ( Aluminium oxide) Rutile is a Mineral composed primarily of Titanium dioxide, Ti[[oxygen O]]2 [4] It can also occur in garnet, diopside and spinel. The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives Diopside is a Monoclinic Pyroxene Mineral with composition MgCaSi2O6 The spinels are any of a class of Minerals of general formulation XY2 O 4 which Crystallize in the cubic (isometric
Chatoyancy
Chatoyant minerals display luminous bands, which appear to move as the specimen is rotated. Tiger's eye (also Tigers eye, Tiger eye) is a chatoyant Gemstone that is usually yellow- to red-brown with a silky luster. In Gemology, chatoyancy (or chatoyance) is an optical reflectance effect seen in certain Gemstones Coined from the French "oeil de chat" Such minerals are composed of parallel fibers (or contain fibrous voids or inclusions), which reflect light into a direction perpendicular to their orientation, thus forming narrow bands of light. The most famous examples are tiger's eye and cymophane, but the effect may also occur in other minerals such as aquamarine, moonstone and tourmaline. Tiger's eye (also Tigers eye, Tiger eye) is a chatoyant Gemstone that is usually yellow- to red-brown with a silky luster. The Mineral or Gemstone chrysoberyl, not to be confused with Beryl, is an aluminate of Beryllium with the formula BeAl2O4 Aquamarine (Lat aqua marinā, "water of the sea" is a Gemstone -quality transparent variety of Beryl, having a delicate blue or Turquoise Moonstone is typically a potassium aluminium silicate, with the chemical formula KAlSi3O8 Tourmaline is a Crystal Silicate mineral compounded with elements such as Aluminium, Iron, Magnesium, Sodium, Lithium
Schiller
Schiller is a term used to describe the colourful iridescence that occurs when light is reflected between layers. Labradorite ((CaNa(AlSi4O8 a Feldspar Mineral, is an intermediate to calcic member of the Plagioclase series It is seen in moonstone and labradorite. Moonstone is typically a potassium aluminium silicate, with the chemical formula KAlSi3O8 Labradorite ((CaNa(AlSi4O8 a Feldspar Mineral, is an intermediate to calcic member of the Plagioclase series
See also
References
- ^ a b c d e f Rudolf Duda, Lubos Rejl (1990). In Gemology, chatoyancy (or chatoyance) is an optical reflectance effect seen in certain Gemstones Coined from the French "oeil de chat" Hornblende is a complex inosilicate series of Minerals Hornblende is not a recognized mineral in its own right but the name is used as a general or field term to Minerals of the World. Arch Cape Press. ISBN 0-517-68030-0.
- ^ Rosie Hankin (1998). Rocks, Crystals & Minerals. Quintet Publishing. ISBN 1-86155-480-X.
- ^ a b Optical properties of Rocks and Minerals. Retrieved on 2008-06-01. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 193 - Roman Emperor Didius Julianus is Assassinated 987 - Hugh Capet is elected
- ^ Emsley, John (2001). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press, pp. 451 – 53. ISBN 0-19-850341-5.
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