Question

.What type of lustre is described as having a "shine like grease applied on the mineral"?

• A. Resinous Lustre
• B. Greasy Lustre
• C. Silky Lustre
• D. Pearly Lustre

Answer 1

Answer:

B. Greasy Lustre

Mineral Lustre - Greasy Lustre

• Greasy Lustre is a type of mineral lustre characterized by its resemblance to the shine of a greasy or oily surface.

• When light reflects off a mineral with a greasy lustre, it appears as if a thin film of oil or grease has been spread across its surface.

• This optical effect is due to the microscopic texture of the mineral's surface, which causes diffuse reflection similar to that seen on a greasy object.

• Minerals exhibiting greasy lustre often appear somewhat transparent or translucent, even if they are opaque in bulk.

• Examples of minerals that commonly display greasy lustre include:

  • Opal: Especially common opal varieties.

  • Sulphur: Native sulphur can exhibit this lustre.

  • Quartz: Some varieties of quartz, particularly those with a rough or altered surface.

  • Serpentine: Certain serpentine minerals.

  • Calcite: Some forms of calcite.

• In geological and mineralogical studies, identifying lustre is a key characteristic used in the preliminary identification of unknown mineral samples.

• Other types of mineral lustre include metallic, vitreous (glassy), pearly, silky, resinous, and dull (earthy).