Glassy mineral is a term used to describe minerals that have a glassy or vitreous luster, meaning they appear shiny and translucent. The four crossword solutions for this term are Spinel (6 letters), FELDSPAR (8 letters), MICA (4 letters), and SILICA (6 letters). Spinel is a mineral composed of magnesium and aluminum oxide, FELDSPAR is a group of minerals containing aluminum, SILICA, oxygen, and potassium, MICA is a group of minerals composed of silicate sheets, and SILICA is a mineral composed of silicon and oxygen.