A harder mineral will scratch a softer mineral, but not vice versa. Quartz will scratch steel and glass, but calcite will not. Steel will scratch calcite, but it may not scratch feldspar. Talc and gypsum can both be scratched with a fingernail. Some Common Minerals 1.
Pure quartz is transparent and colorless.
Any color can result from impurities. Quartz is often found as small sand particles or in microcrystalline form, but it can also form huge six-sided crystals with pyramidal points. Feldspar - Feldspars are the single most common mineral family in the earth's crust. The feldspar found in central Texas is easily recognized by its pink color. White feldspar is also common.