Usually either as small elongated striated prisms or as long, slender, delicate acicular needles, black in color, radiating out from a common center. Most crystals are under 0.25 inches (6mm) in length, however, may reach a length of up to 3.5 inches (8.5cm).
Pseudobrookite is a rare mineral found at only a few other locations in the world. The crystals occur as two types. Crystals of Type I occur throughout the range. They consist of minute striated prisms generally perched on cavity walls or inter-grown with topaz, red beryl, bixbyite or garnets. Type I is mineralogically interesting, but of little interest to the collector.
Type II consists of black (sub-metallic), delicate acicular crystals in cluster form with the crystals being attached to the lithophysal wall near a common point and radiating outward into the open cavity. At one locality in the Thomas Range specimens with individual crystals up to 3 1/2 inches in length have been collected; however, crystals seldom exceed one inch in length; 0.25 inch being about average.
Type II pseudobrookite is also associated, and even inter-grown, with topaz. In some specimens, the pseudobrookite crystals grow right through the topaz. Specimens of this type are strikingly beautiful and highly desired by collectors. People often mistake pseudobrookite for the black tourmaline schorl particularly type I; tourmaline does occur in the Thomas Range but so far only as microscopic crystals.
