is pink quartz difficult to find, or is it expensive?
Hornblende. Quartz is harder and some of the elements that make up hornblende are more likely to chemicly react with the atmosphere than the silicon and oxygen that make up quartz
The susceptibility of minerals to weathering is more or less the inverse of the Bowen Reactions Series: The scale is called the Goldich Stability series, and on that series quartz is the most stable (least susceptible to weathering). Amphiboles and pyroxenes which contain iron and magnesium are much more reactive under weathering conditions. This is becuase they are very unstable at the earth's surface, and will react readily with acid ground waters to form clay minerals.
