+ How are Minerals Identified?
Luster describes the way light reflects off of the surface of the mineral. You might describe diamonds as sparkly or pyrite as shiny. But mineralogists have special terms to describe luster. They first divide minerals into metallic and non-metallic luster. Minerals that are opaque and shiny, like pyrite, are said to have a “metallic” luster. Minerals with a “non-metallic” luster do not look like metals. There are many types of non-metallic luster. Six are described in Table.
|Resinous||Like resins, such as tree sap|
|Silky||Soft-looking with long fibers|
Can you match the minerals in Figure with the correct luster from Table without looking at the caption?
(A) Diamonds have an adamantine luster. These minerals are transparent and highly reflective. (B) Kaolinite is a clay with a dull or earthy luster. (C) Opal’s luster is greasy. (D) Chalcopyrite, like its cousin pyrite, has metallic luster. (E) Stilbite (orange) has a resinous luster. (F) The white ulexite has silky luster. (G) Sphalerite has a submetallic luster. (H) This Mayan artifact is carved from jade. Jade is a mineral with a waxy luster.