|A red corundum that contains chromium impurities is ____.
|A purple quartz that contains manganese impurities is ____.
|Pure ____ (SiO2) is colorless and has a hardness of 7.
|The minerals diamond and ____ are pure carbon allotropes.
|The hardest naturally-occurring mineral is ____ (hardness 10).
|The mineral form of sodium chloride (NaCl) is ____ (rock salt).
|A green beryl that contains chromium impurities is ____.
|The mineral ____ (FeS2) is also known as Fool's Gold.