PSEUDOBROOKITE Fe2 O3 Ti O2
Crystal Description: Orthorhombic
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, they have reached lengths of up to 3.5 inches (8.5cm).
Physical Properties:
Color- Black
Luster- Metallic
Hardness- 6 – 6.5
Cleavage- None
Pseudobrookite is a rare mineral found at only a few other
locations in the world. The crystals consist of two types. Crystals of
Type I occur throughout The Cove. They consist of minute striated
prisms generally perched on cavity walls or inter-grown with topaz,
red beryl, bixbyite, and garnets. Type I is mineralogically interesting,
but of very little interest to the collector.
Type II pseudobrookite 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 specimens up to 3 1/2 inches have been
collected; however, in The Cove, crystals seldom exceed one inch in
length with 0.25 inch being about average.
There are two areas, in The Cove, where good specimens of
Type II can be collected. See Maps 5 and 6. At both localities, good
specimens can be obtained with a little work. Because of their delicate
nature, weathered crystals disintegrate, and it is therefore necessary to
collect them in place by breaking rock.
Type II pseudobrookite is also associated with and intergrown
with topaz. In some specimens, pseudobrookite crystals grow directly
through the topaz. Specimens of this type are strikingly beautiful and
highly desired by collectors.