THE MINERAL PYROLUSITE
- Chemical Formula: MnO2, Manganese Oxide
- Class: Oxides and Hydroxides
- Group: Rutile
- Uses: a major ore of manganese and as a mineral specimen
Specimens
Pyrolusite is an oxidation product of weathered manganese minerals and also forms from stagnant shallow marine and freshwater bog and swamp deposits. Minerals such as rhodochrosite, rhodonite and hausmannite are often replaced by pyrolusite.
Pyrolusite has some interesting habits despite its common occurrence as dull, sooty, black masses and/or earthy forms. Possibly its most popular form is its dendritic habit that forms wonderfully detailed, fern-like patterns on the surfaces of rocks such as sandstone. These dendrites are so amazing that they have often been mistaken for fossil plants. Another popular habit is its acicular or hair-like crystal aggregates that produce nice tufts of "hair", or meadows of shiny black pyrolusite fibers. Often specimens of pyrolusite are very difficult to distinguish from other manganese oxides. Thus, as a consequence of its more abundant distribution, pyrolusite is the default name for black, hair-like manganese crystals or powdery black alteration products of manganese minerals in general.
PHYSICAL CHARACTERISTICS:
- Color is steel gray to a solid black in earthy specimens.
- Luster is metallic to dull in weather or thinly crusted specimens.
- Transparency crystals are opaque, translucent in only thin splinters.
- Crystal System is tetragonal; 4/m 2/m 2/m
- Crystal Habit is typically massive and compact forms, but also fibrous, acicular, columnar, concretionary, scaly and earthy forms are well known. A thin dendritic habit is commonly seen encrusted on sandstones and siltstones and will form wonderful fern or tree like patterns that are often mistaken for fossil plants. A variety with large, easily visible crystals is called polianite, and occurs as minute prismatic crystals with a square or rectangular cross-section and a wedge-shaped terminations.
- Cleavage is good in two directions forming prisms, but rarely seen except in rare large crystals.
- Fracture is conchoidal to uneven.
- Hardness is 6 in individual crystals, but aggregates can be as soft as 4 or 5 and massive or earthy forms will mark paper and leave powder on fingers (a hardness under 2).
- Specific Gravity is 4.4 - 5.1 (average for metallic minerals)
- Streak is black.
- Associated Minerals are limonite, hematite, quartz, manganite, psilomelane and other manganese and iron oxide minerals.
- Notable Occurances include nice specimens from Germany; iron mines in Minnesota and Michigan and at Lake County, New Mexico, USA. Pyrolusite is mined in many countries around the world with the most productive countries being Georgia and Ukraine of the former USSR, India, China, South Africa, Brazil, Australia and Gabon. Polianite occurs in abundance at the Kisenge Mine, in Zaire.
- Best Field Indicators are habits, luster, softness, color and streak.
 Amethyst Galleries' Mineral Gallery MINERALS |
PYROLUSITE specimen pyl-4$ 75.00
Dims: 2.4" x 2.3" x 1.6"(6.1 x 5.8 x 4.1 cm)
Wt: 6.06 oz.(172.0 g)
Kisenge Mine, Zaire
On a heavy botryoidal base of various manganese oxides rest hundreds of small crystals of Polianite, a variety of Pyrolusite that has unusually large, thick crystals. These crystals are only about 2 x 1 x 1 mm in dimensions, but it is enough so that one can easily see their prismatic form, square-to-rectangular cross-sections, and wedge-like terminations without a loupe or magnifier. The crystals and their base are colored a dark gray (polianite from the Greek word polia, meanging "grayness", in allusion to its color), have a submetallic luster, and are opaque. There is a moderate amount of damage in the form of crushed crystals and broken botryoidal formations. The base rock is also made up of Pyrolusite, and strongly resembles formations of psilomelane, showing layers of material that are alternately waxy and metallic in luster. It is the first piece of this particular variety that I have ever seen.
pyl-4 ($ 75.00)Kisenge Mine, Zaire
PYROLUSITE specimen pyl-5
$ 30.00
$ 30.00
Dims: 2.6" x 1.5" x 0.9"(6.6 x 3.8 x 2.3 cm)
Wt: 2.76 oz.(78.4 g)
Kisenge Mine, Zaire
On a botroidal bed that looks a lot like psilomelane, several dozen minute Polianite crystals rest in a cluster. Like Pyrolusite(which it is a variety of), the Polianite has a dark gray color, metallic to waxy luster, and is opaque. The difference, however, is in the crystals. The Polianite occurs in well-formed tetragonal prisms with wedge-shaped terminations. Though they are small(2 x 1 x 1 mm maximum), their crystal form is visible to the naked eye, although magnification will help considerably. The botryoidal base is made up of Pyrolusite, and possibly other manganese oxide minerals.
pyl-5 ($ 30.00)
Kisenge Mine, Zaire
PYROLUSITE specimen pyl-7
$ 35.00
$ 35.00
Dims: 4.4" x 3.4" x 2.2" (11.2 x 8.6 x 5.6 cm)
Wt: 1 lb., 6.6 oz. (641 g)
Aouli, Morocco
The brown-red host rock of this specimen is littered with sprays of long, thin Pyrolusite crytals that are flattened against it. The Pyrolusite crystals achieve lengths of nearly 1" (2.5 cm) and are arranged in radial sprays, some of which extend 360 degrees. There are also some rather strange, round formations that are exposed on the other side of the specimen. They are broken off at the surface, so I cannot tell whether or not they were in a botryoidal habit, but I don't believe that they were. There is a substantial amount of calcite on the host rock; I cannot identify the host rock itself. This is one of the largest Pyrolusite specimens that we have in our present stock.
pyl-7 ($ 35.00)
Aouli, Morocco
PYROLUSITE specimen pyl-8
$ 90.00
$ 90.00
Dims: 2.6" x 2.0" x 1.6" (6.6 x 5.1 x 4.1 cm)
Wt: 5.82 oz. (165.0 g)
Mina Los Belones, La Union, Murcia, Spain
This is one of the stranger and more attractive Pyrolusite specimens that I have come across. It consists of a thin crust of Pyrolusite that covers a crystal formation of barite. There are some semicrystalline formations of the Pyrolusite, though; the upper edges of the two largest barite crystals are lined with tiny "puffs" of round, radiating pyrolusite formations, and several larger ones on lesser crystals. The material is generally colored black, though some appears to have a dark gray color, and all has a very dull luster and is opaque. The barite crystals that the Pyrolusite coats have excellent orthorombic form that is quite easily visible due to the Pyrolusite's dark color and dull luster. The two largest crystals may have started out as one single crystal and then broke apart and were partially healed. Other, smaller crystals sprout off of their sides, which show many small formations and growth patterns. It is one of a few minerals that we stock which were mined in Spain.
pyl-8 ($ 90.00)
Mina Los Belones, La Union, Murcia, Spain
PYROLUSITE specimen pyl-9
$ 20.00
$ 20.00
Dims: 1.7" x 1.2" x 1.0" (4.3 x 3.0 x 2.5 cm)
Wt: 1.45 oz. (41.0 g)
Kisenge Mine, Zaire
This large thumbnail specimen consists of a small chunk of Pyrolusite that shows mostly massive and botryoidal form. Much of its surface is caused by its separation from its place of formation, but a substantial portion shows excellent botryoidal form, with intergrown nodules of a relatively uniform size and arrangement. A few tiny hollows extend into the breakage surfaces; these are lined with tiny crystals of a variety of Pyrolusite that is known as Polianite, which forms crystals that are generally thicker and more substantial than regular Pyrolusite crystals. All of the Pyrolusite has a dark gray color and a dull to moderate metallic luster. There is no other material or host rock on the specimen.
pyl-9 ($ 20.00)
Kisenge Mine, Zaire
PYROLUSITE specimen pyl-10
$ 30.00
$ 30.00
Dims: 1.6 x 1.3 x 0.9" (4.1 x 3.3 x 2.3 cm)
Wt: 1.3 oz. (37.1 g)
Kisenge Mine, Zaire
This thumbnail specimen consists entirely of Pyrolusite, in both a massive and crystalline form. The crystals take the form of tiny tetragonal blades that do not exceed 2 mm in any dimension, but are in generally excellent condition, showing very little damage except around their edges. All have a dark gray-black coloration and a dull metallic luster. The massive material has similar properties, but no discernable form. It does, however, contain some tiny reniform formations on the surface that is opposite that which the crystals coat.
pyl-10 ($ 30.00)
Kisenge Mine, Zaire
PYROLUSITE specimen pyl-11
$ 30.00
$ 30.00
Dims: 2.1 x 1.0 x 0.9" (5.3 x 2.5 x 2.3 cm)
Wt: 1.4 oz. (40.7 g)
Kisenge Mine, Zaire
I think that the crystals on this Pyrolusite specimen are a bit to small for me to be able to call them "Polianite" crystals, but that is what they were purchased as. They are extremely small, with visible dimensions that do not exceed 1 mm. All appear to be in good condition, though there are a few small areas in which the crystals have been noticeably crushed. Magnification is necessary to study their tetragonal prismatic form, which is quite good; each crystal has well-defined edges and smooth faces that possess a bright submetallic luster. All have a dark gray-black coloration with subtle brown highlights. This crust is one of a few layers that rest on a more massive base of Pyrolusite. The layering has caused the crusts to take on a reniform habit.
pyl-11 ($ 30.00)
Kisenge Mine, Zaire
PYROLUSITE specimen pyl-12
$ 60.00
$ 60.00
Dims: 4.2 x 1.7 x 1.1" (10.7 x 4.3 x 2.8 cm)
Wt: 7.2 oz. (203 g)
Baraga County, Michigan, U.S.A.
Several intergrown clusters of Pyrolusite crystals make up this hand specimen. The largest cluster contains crystals that reach 3.3" (8.3 cm) in length, but most of the other clusters are much smaller. None of the crystals have definite tetragonal form- they are more columnar, compact, and fibrous in habit. All have the black-gray color and metallic luster of their specie, and are attached to, if not embedded in, a massive chunk of colorless quartz.
pyl-12 ($ 60.00)
Baraga County, Michigan, U.S.A.
PYROLUSITE specimen pyl-13
$ 35.00
$ 35.00
Dims: 2.3 x 1.7 x 1.0" (5.8 x 4.2 x 2.6 cm)
Wt: 2.14 oz. (60.7 g)
Old Taylor Mine, Alberta, Michigan, U.S.A.
Many intersecting clusters of compact, radial Pyrolusite needles are embedded in the brown host rock of this hand specimen. Though most of these clusters are incomplete, their surfaces show the compact, radiating habit of the needles quite well. All have a dark gray color and a dull metallic luster. The quartzite base is brown in color, likely due to iron oxide inclusions, and has many hollows, some of which are coated with druses of tiny quartz crystals.
pyl-13 ($ 35.00)
Old Taylor Mine, Alberta, Michigan, U.S.A.
PYROLUSITE specimen pyl-14
$ 25.00
$ 25.00
Dims: 1.8 x 1.4 x 1.1" (4.7 x 3.5 x 2.7 cm)
Wt: 1.77 oz. (50.1 g)
Aouli, Morocco
This small hand specimen consists of a brown host rock that is permeated with veins of Pyrolusite. One such vein is exposed, showing the compact, radial habit, gray color and metallic luster of the mineral. There are no individual crystals to study, but their tetragonal form is likely good.
pyl-14 ($ 25.00)
Aouli, Morocco