This refers to the overall appearance of a mineral, in particular how shiney it is. Generally the harder the mineral the more shiney it is e.g. pyrite measures 6 on the mohs scale and is shiney gypsum is 2 on the mohs scal and is not shiney.

 

Minerals and gemstones are classified as one of the following. Therefore observing their appearance may help with identification.

Earthy e.g. marble

Greasy e.g. moss agate

Silky e.g. serpentine

Pearly e.g. nacre

Resinous (sticky) e.g. amber

Adamantine e.g.diamond

Vitreous (glass like) e.g. spodumene