Step 1 : Introduction to the question "2. Rock crystal is a clear transparent variety of which common mineral?"
...1. Quartz 2. Garnet 3. Feldspar 4. Olivine Quartz occurs in all the three types of rocks - igneous, sedimentary and metamorphic. With a hardness of 7 on the Mohs scale, the mineral is quite resistant to weathering and hence commonly found in sedimentary deposits. Traces of different elements produce different varieties of quartz which are categorized based on their colour. Another variety of quartz which would've fit the theme of this quiz is rose quartz - a pink variety whose colour is generally attributed to small amounts of titanium or manganese found in the mineral. Corporal Slag favours the purple variety better known as the gem stone, amethyst.