Concept:
Polymorphism means the ability of a substance to exist in more than one crystalline form while having the same chemical composition.
Step 1: Quartz is a crystalline form of silica:
\[
SiO_2
\]
Step 2: Silica can exist in different polymorphic forms depending on temperature and structure.
Step 3: The main polymorphic forms of silica are:
\[
\text{Quartz, Tridymite, and Cristobalite}
\]
Step 4: Therefore, the total number of important polymorphic forms of quartz/silica is:
\[
3
\]
Hence,
\[
\boxed{3}
\]