Some crystals can grow to a fairly large size of several feet long and nearly a foot across. Other specimens of hornblende can be acicular clusters or needle thin crystal aggregates. Many times a specimen of a more valuable mineral will be accented by the opaque black crystals of hornblende. Color is almost always black to dark green. Luster is vitreous to dull.
Crystals are generally opaque but thin crystals or exceptional specimens can be translucent.
Crystals can have a hexagonal cross-section although rarely symmetrical. The typical termination, if seen, appears as the two faces of a dome but is actually two of the four faces of a prism. Also found granular, massive and occassionally acicular aggregates. Cleavage is imperfect in two directions at 56 and 124 degrees. Fracture is uneven.