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