The way light bounces off a mineral's surface is described by the mineral's _____.  

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The way light bounces off of a mineral's surface is described as its luster. There are a number of specific descriptions or categorizations for a mineral's luster. Do keep in mind that luster is related to the opacity/transparency of a mineral in addition to the surface conditions, crystal habit, and...

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The way light bounces off of a mineral's surface is described as its luster. There are a number of specific descriptions or categorizations for a mineral's luster. Do keep in mind that luster is related to the opacity/transparency of a mineral in addition to the surface conditions, crystal habit, and index of refraction. Luster is unrelated to the color of a mineral or gem.

  • Dull, or earthy. This describes minerals with a matte surface, or one that is not shiny. Chert and flint fall into this category.
  • Waxy, or waxlike. These minerals may look like they have a coating of wax, and can be a little bit reflective. Coral and serpentine fall into this category.
  • Pitchy, or pitchlike. This means that a mineral looks similar to tar. Many radioactive minerals like uranininite fall into this category.
  • Greasy, like the mineral has been covered in an oily substance. Opal falls into this category.
  • Pearly, or mother-of-pearl sheen, describes minerals which look pearlescent. Muscovite and stilbite are two examples of pearly minerals.
  • Silky minerals look similar to the textile silk. They are composed of very fine fibers. The dangerous mineral asbestos falls into this category.
  • Resinous, or resinlike, describes minerals which look like resin or plastic. Amber is a famous type of resinous mineral, and is actually fossilized resin from a tree.
  • Adamantine, also called brilliant or diamondlike, has a very reflective and refractive luster. Like the name implies, diamonds fall into this category.
  • Vitreous, or glassy, describes minerals which look like glass. The quartz varieties falls into this category.
  • Submetallic minerals are those which look similar to metal but are not as reflective. Sphalerite is a perfect example of a mineral with submetallic luster.
  • Metallic minerals are highly opaque and reflective, like pyrite.
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