The Mineral PSILOMELANE
- Chemical Formula: No fixed formula, but sometimes Ba(Mn+2)(Mn+4)8O16(OH)4 is used, Barium Manganese Oxide Hydroxide
- Class: Oxides and Hydroxides
- Uses: an ore of manganese and as a mineral specimen
Specimens
Psilomelane, although not as common as pyrolusite, is still an important ore of manganese. Manganese is a strategically valuable metal since it is an essential ingredient in steel and other alloys. The mining term "wad" is used to indicate ores that are a mixture of several manganese oxides such as psilomelane, pyrolusite and others that are difficult to distinguish.
Psilomelane is often banded with gray pyrolusite and the alternating layers make an attractive polished stone with bands of metallic gray and submetallic black. Psilomelane also forms tufts of hair-like aggregates that are similar to those produced by pyrolusite. However, the difference in luster between the two minerals is usually sufficient to distinguish them. Earthy specimens as well are difficult to differentiate since both minerals tend to have a dull luster when found in this habit. Fortunately pyrolusite's softness will give it away when it leaves marks on paper and fingers.
PHYSICAL CHARACTERISTICS:
- Color is variable from iron-black to bluish black to steel gray.
- Luster is submetallic to dull in earthy specimens.
- Transparency crystals are opaque.
- Crystal System is monoclinic.
- Crystal Habits include massive, fibrous, botryoidal, columnar, stalactitic, concretionary, powdery and earthy.
- Cleavage is absent.
- Fracture is conchoidal to uneven.
- Hardness is 5 - 5.5.
- Specific Gravity is 4.4 - 4.5 (heavy for non-metallic minerals)
- Streak is black or brownish black.
- Other Properties: sometimes banded with the mineral pyrolusite producing alternating bands of metallic gray and submetallic black.
- Associated Minerals are barite, hematite, quartz, pyrolusite and other manganese oxide minerals.
- Notable Occurances include Austinville, Wythe County., Virginia, Upper Pennisula of Michigan and Tuscon, Arizona, USA; Schneeburg, Germany; Cornwall, England; Ouro Preto, Minas Gerias, Brazil and elsewhere.
- Best Field Indicators are habits, luster, hardness, color and streak.
 Amethyst Galleries' Mineral Gallery MINERALS |
PSILOMELANE specimen psi-1
$ 40.00
$ 40.00
Dims: 2-3/8" x 1-7/8" x 1"
Wt: 2.02 oz
Black Canyon Mine, New Mexico, U.S.A.
What can I say about this specimen, other than that Psilomelane can occupy some bizarre forms? It is made up entirely of Psilomelane-- there is no host rock. The base is made up of compact fibrous layers of the material. This material gets much more fibrous, though, with "tufts" of it covering the compact base! I don't know for sure if each tiny "hair" is a crystal, but I think so! It basically looks like a brown-black slab of base rock that is covered with short, black matted fur!
psi-1 ($ 40.00)
Black Canyon Mine, New Mexico, U.S.A.
PSILOMELANE specimen psi-2
$ 18.00
$ 18.00
Dims: 2-1/2" x 2-1/4" x 1-1/2"
Wt: 4.5 oz
Cooks Range, Luna Co., New Mexico, U.S.A.
I like this specimen; that means that it is kind of weird, usually, and this instance is no exception! It is basically made up of hundreds of intergrown botryoidal globules of Psilomelane. The material has a gray-black color and a matte luster, and is fairly heavy for its porosity. Amidst the globules are patches of crusted quartz, both crystalline and microcrystalline, that show signs of weathering. I really like psilomelane because of its wildly varied range of forms.
psi-2 ($ 18.00)
Cooks Range, Luna Co., New Mexico, U.S.A.
PSILOMELANE specimen psi-3
$ 45.00
$ 45.00
Dims: 3.7" x 2.7" x 2.4"(9.4 x 6.9 x 6.1 cm)
Wt: 1 lb., 2.8 oz.(532 g)
Zigg Zagg Mine, Armer Ranch, Gila County, Arizona, U.S.A.
Composed almost entirely of Psilomelane, this specimen consists of a heavy base of the material out of which have grown tall botryoidal formations, like tight clusters of tiny grapes. The color of the material is black, of course, and it has a waxy to dull luster. Several of the botryoidal globules are damaged, and one can see a very tightly-packed acicular, radial habit in the cross-sections that the damage forms. This habit is also visible on the sides of the base, where the piece was separated from its place of origin. Along the largest of these breakage faces are a few patches and hollows where the Psilomelane takes on a satiny luster, due to the presence of thousands of individual microscopic crystals terminating on the surface. The underside of the specimen shows some rust staining and a tiny bit of what I think is a sandstone host. One could conceivably polish the sides and bottom of this specimen to make a truly unique decoration for a shelf or curio cabinet.
psi-3 ($ 45.00)
Zigg Zagg Mine, Armer Ranch, Gila County, Arizona, U.S.A.
PSILOMELANE specimen psi-4
$ 40.00
$ 40.00
Dims: 1.1" x 0.9" x 0.4" (2.8 x 2.3 x 1.0 cm)
Wt: 8.8 g
Unknown (likely Mexico)
This small piece consists of a polished Psilomelane stone that has a nearly symmetrical isosceles triangular shape. One can see its metallic gray and black layering very well, and its hand-cut form makes them form some interesting patterns. I have found a few vendors at some of the larger shows that sell this material in rough form and several that sell cut pieces of "black drusy quartz", but almost nobody sells cut stones that show the layering like this one.
psi-4 ($ 40.00)
Unknown (likely Mexico)
PSILOMELANE specimen psi-5
$ 110.00
$ 110.00
Dims: 5.0" x 3.2" x 3.0" (12.7 x 8.1 x 7.6 cm)
Wt: 1 lb., 12.4 oz. (806 g)
Manganese District, Grant County, New Mexico, U.S.A.
This large hand specimen consists of a dull, pale brown host rock through which extend several layers of compact Psilomelane. There are also a few crusts of the material that coat portions of its surface. Many of the more exposed layers and crusts show considerable damage, but this damage allows one to see their cross-sections and their almost compact, fibrous habit. A few of the crusts that coat the host rock have a sparkly sheen on their outer surfaces that suggest that they are encrusted with tiny crystals, likely made of quartz. The veins and crusts are layered, showing alternate bands of material that have black and metallic gray colors- cross-sections of a few of the thicker veins show patterns that look like plumose or dendritic formations. The host rock appears to be made up partly of a conglomerate of irregularly-sized and shaped rocks in a finely-grained matrix and layers of a gray flint or chert made of alternating bands of pale and darker brown material.
psi-5 ($110.00)
Manganese District, Grant County, New Mexico, U.S.A.