Quartz with Brookite
The brookite is one of the three Titanium Dioxide (TiO2) crystal forms together with anatase and rutile which is the most common.
At temperature of 750C°brookite will revert to rutile structure. His hardness and density are much the same as rutile ,but differ in cleavage and crystal habit which are often tabular or like needles with pseudo-hexagonal outline. In this case the brookite blades acted as nuclei for the crystallization of rutile like silver needles.