Here's why:

* Foliation is a planar or layered structure in metamorphic rocks that results from the alignment of mineral grains under pressure. It's often seen in rocks like slate, schist, and gneiss.

* Quartzite forms when sandstone is metamorphosed. Sandstone is made up of quartz grains, which are very hard and resistant to deformation.

* During metamorphism, the quartz grains in sandstone recrystallize and interlock, forming a very strong, hard rock. This recrystallization process does not lead to the alignment of minerals necessary for foliation.

Instead of foliation, quartzite might exhibit:

* Banding: This is due to the original layering in the sandstone, which can be preserved in the quartzite.

* Fracturing: Quartzite is very hard and brittle, so it often breaks along fractures rather than showing foliation.

Let me know if you have any other questions about metamorphic rocks!