Brookite is one of the three main polymorph forms of TiO2, three minerals with the same composition but different structure, rutile and anatase being the other two.
Brookite is the most rare of the three and usually occurs in very fragile crystals of a nice red colour with a refractive index higher than diamond. Is a typical mineral of alpine type hydrothermal vein and for this reason is often included in quartz. In this case quartz preserve its beauty and its fragility. Most of the brookite included in quartz is strictly associated with rutile, often of silver colour, more rarely golden. The association is a clear epitaxy with rutile needles crossing the brokite blade with an angle of 60 degres. So the brookite crystal is often masked by the rutile fibers and quite rarely it appear rutile free.
Main deposit of cutting quartz material with brookite inclusions comes from the area of Diamantina, Jequitinhonha Valley, between Gouveia and Corinto, in Minas Gerais, Brazil. Also good brookites in quartz have appeared on the market from Pakistan, but the production is more directed to collector crystal than to cutting rough.

Left: Brookite and silver Rutile from Brazil. Right: Brookite and golden Rutile, Pakistan