Psilomelane is softer than quartz, about a 5 to a 6 on Mohs scale. It's often found in grape-like botryoidal formations, but you can see this unusual psilomelane sample that formed with black hair-like crystals on the top. That's a very close-up look: the crystals are less than a quarter-inch tall!
Besides the Silver Crown Mine in Chihuahua, Mexico, there aren't many active centers of gem-grade psilomelane mining. Augusta County, Virginia once had a mine, Crimora, which is now abandoned. Psilomelane has also been found in Arizona, New Mexico, Montana, and Arkansas in the US, and in small pockets of Europe, Africa, Asia, Australia, and Europe.
Sometimes you will see psilomelane stones that have clear parts between the "grain," even druzy sometimes. (See an example here, courtesy of GreatRough.com) This clear area is chalcedony, and some call it manganese oxide in quartz. Chalcedony psilomelane can turn into beautiful cabochons.
Metaphysically speaking, psilomelane is said to aid in understanding our emotional patterns and empowering us to re-engrave those grooves.