What is luster of a mineral

Properties of Minerals: Luster - Expii Luster is the property of minerals that describes how light is reflected. Metallic, waxy, vitreous, silky, pearly, and dull are all types of luster.

Properties of Minerals: Luster. Go to Topic. Explanations 1. Luster Luster is the property of minerals that shows how much or how well the mineral reflects light. Most types of luster are self-explanatory. Metallic: The mineral shines like a metal. Amber, sphalerite , almandine garnet , and some specimens of sulfur exhibit a resinous luster. Specimens with a resinous luster are usually yellow, orange, red, or brown in color.

Silky Luster: A specimen of satin spar gypsum with the reflective fibrous structure that produces a silky luster. Some mineral specimens are composed of many parallel fibers or parallel crystals that are bound together and reflect light.

This produces a luster that is similar to the light reflected from a bundle of parallel silk threads. The satin spar variety of gypsum is an excellent example of a silky luster.

Tiger's-eye , chrysotile serpentine , tremolite, and ulexite can also exhibit a silky luster. The tourmaline crystals in the first image at the top of this page have a silky luster produced by parallel striations on prismatic crystals. Waxy Luster: Three cabochons of various types of serpentine that produce a waxy luster from their polished surfaces. The polish is not bright.

Instead it is a soft glow. Materials that have a waxy luster have an appearance that is similar to the surface of a candle, a block of beeswax, or a piece of paraffin.

Some specimens of talc , serpentine , rough opal , jade , and the conchoidal fracture surfaces of agate are examples of materials with a waxy luster.

Materials with a waxy luster are usually translucent, and direct light upon them produces a soft waxy glow. Adamantine Luster: An octahedral diamond crystal in positive relief on the surface of its host rock. Adamantine is the highest level of luster. This diamond crystal is estimated to be approximately 1. Adamantine is the highest luster observed in minerals. It is a luster that is similar to vitreous, but the adamantine specimens are more reflective.

There is no sharp division between a vitreous luster and an adamantine luster. When a specimen has a luster that is difficult to assign to one of these categories, the term subadamantine might be suitable. Some specimens of diamond , cassiterite , corundum , sphalerite , cerussite, vanadinite , titanite , malachite , rutile , and zircon exhibit an adamantine luster.

Many minerals used in commercial products owe their value and popularity at least in part to their luster. The best example is gold. It has a highly reflective metallic luster that resists tarnish. That beautiful luster makes gold the perfect metal for jewelry manufacturing. Today, most of the world's gold is made into jewelry. Muscovite mica is another mineral that is used commercially because of its luster. Its highly reflective, eye-catching pearly luster, along with its ability to be ground into tiny, flat flakes, makes it the perfect additive in a variety of products.

Minute flakes of muscovite bring a glittery appearance to cosmetics, paints, plaster, plastics, tile, pottery glazes, and many other products that people use or see every day. Luster is not a diagnostic property. This means that, for most mineral species, luster can vary from one specimen to another. For example: hematite can exhibit a metallic luster, a submetallic luster, or a dull luster.

A single specimen can exhibit one or more of these lusters. Because of that, luster cannot be heavily relied upon in mineral identification. It might be considered to be a "hint" that can set a person on the proper route. Most geologists, including the author of this article, have not thought as deeply about luster as gemologists. If you open almost any mineralogy textbook to the pages that describe a mineral, the luster is usually given as one or two of the adjectives listed above.

For example: submetallic to metallic. Most minerals with a dull luster have a rough or porous surface. Every mineral has a characteristic luster, but some minerals may have a different luster on different specimens. There is no scientific method to determine luster. Often, determining the luster of a particular specimen is personal; to some it may appear as one type of luster, and to others as a different type. It is in the eyes of the viewer to determine what luster a particular specimen exhibits.

Luster is only a useful form of mineral identification when the specimen in question displays a unique luster, such as waxy, greasy, pearly, etc. Specimens with a vitreous luster cannot be distinguished from one another, nor can minerals with a metallic luster. Luster is usually just noted as a mineral property, and is not commonly usually used to help identify a mineral. Observe the specimen in well lit conditions where its luster is visible. Quartz is said to have a glassy or vitreous luster, but its color may be purple, rose, yellow, or any of a wide range of hues.

The different types of luster referred to are: Metallic , having the look of a polished metal;. Submetallic , having the look of a metal that is dulled by weathering or corrosion; and. Non-metallic , not looking like a metal at all. Nonmetallic luster is divided into several sub-types: Adamantine, having the hard, sparkly look of a diamond;.

Pearly, having the iridescent look of mother-of-pearl though usually just barely ; often found on the cleavage face of a mineral having perfect cleavage.