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Lustre (British English) or luster (American English; see spelling differences) is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin lux , meaning "light", and generally implies radiance, gloss, or brilliance.
When using the chart, it is important to remember these tips: Isotropic and opaque (metallic) minerals cannot be identified this way. The stage of the microscope should be rotated until maximum colour is found, and therefore, the maximum birefringence. Each mineral, depending on the orientation, may not exhibit the maximum birefringence.
The most common mineral inclusion in peridot is the chromium-rich mineral chromite. Magnesium-rich minerals also can exist in the form of pyrope and magnesiochromite. These two types of mineral inclusions are typically surrounded "lily-pad" cleavages. Biotite flakes appear flat, brown, translucent, and tabular. [16]
Micas are translucent to opaque with a distinct vitreous or pearly luster, and different mica minerals display colors ranging from white to green or red to black. Deposits of mica tend to have a flaky or platy appearance. [10]
Chalcedony has a waxy luster, and may be semitransparent or translucent. It can assume a wide range of colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown ranging from pale to nearly black. The color of chalcedony sold commercially is often enhanced by dyeing or heating. [4]
Many minerals may present a variety of colors, in the same or different rocks, or even multiple colours in a single mineral specimen called colour zonation. For example, the mineral tourmaline may have concentric zones of colour ranging from brown, yellow, pink, blue, green, violet, or grey, to colorless.
The analysis can show which minerals tend to coexist and what conditions (geological, physical, chemical and biological) are associated with them. This information can be used to predict where to look for new deposits and even new mineral species. [28] [29] [30] A color chart of some raw forms of commercially valuable metals. [31]
Color: Transparent to translucent, usually green, less often colorless, yellow, blue to violet, pink, brown. [3] Crystal habit: Tabular, prismatic crystals, massive, compact or granular: Cleavage [0001] indistinct, [1010] indistinct [2] Fracture: Conchoidal to uneven [3] Mohs scale hardness: 5 [3] (defining mineral) Luster: Vitreous [3] to ...