The term REDDISH MINERAL can be summarized by two crossword solutions: JASPER and Spinel. JASPER is an opaque, impure variety of quartz that is usually red, yellow, or brown in color. It often contains organic material and mineral oxides which give it interesting patterns. Spinel is a mineral composed of magnesium aluminum oxide, and is usually found in shades of red, pink, blue, violet, and black. It is often used as a gemstone and is known for its hardness and durability.