• Chemical Formula: MnO2, Manganese Oxide.
  • Class: Oxides and Hydroxides
  • Uses: A minor ore of manganese and as a mineral specimen.
  • Specimens

Ramsdellite is a rather uncommon mineral to be seen in mineral markets. Partly because of its rarity, partly because of its general lack of good crystals and partly because of its difficulty in being identified. Ramsdellite is polymorphous (meaning many shapes) with the relatively common mineral pyrolusite. The two minerals have the same chemistry, but different structures. Pyrolusite is tetragonal and ramsdellite is orthorhombic. A third mineral, akhtenskite, is much more rare than these two and is also a polymorph being hexagonal. The three minerals are thus referred to as trimorphs.

Ramsdellite is an oxidation product of weathered manganese minerals, such as manganite. Ramsdellite is often a minor constituent of "Wad". The mining term "wad" is used to indicate massive ores that are a mixture of several manganese oxides such as pyrolusite, psilomelane, ramsdellite and others that are difficult to distinguish. Manganese is a strategically valuable metal since it is an essential ingredient in steel and other alloys.


  • Color is black to gray.
  • Luster is metallic to dull.
  • Transparency: Crystals are opaque, translucent in only thin splinters.
  • Crystal System is orthorhombic; 2/m 2/m 2/m
  • Crystal Habit is typically massive and granular. Crystals are uncommon and tabular.
  • Cleavage is good , but rarely seen except in rare large crystals.
  • Fracture is conchoidal to uneven.
  • Hardness is approximately 3, but is variable.
  • Specific Gravity is 4.4 - 4.8 (average for metallic minerals)
  • Streak is black.
  • Associated Minerals are limonite, hematite, quartz, manganite, psilomelane, pyrolusite and other manganese and iron oxide minerals.
  • Notable Occurrences include nice specimens from Germany; former Czechoslovakia; Lake Valley, New Mexico, Minnesota, California and Montana, USA.
  • Best Field Indicators are habits, luster, softness, color and streak.
RAMSDELLITE specimens:
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RAMSDELLITE specimen ram-1
$ 22.00
Dims: 0.9" x 0.8" x 0.4" (2.3 x 2.0 x 1.0 cm)
Wt: 5.5 g
Mistake Mine, Yavapai County, Arizona, U.S.A.
This specimen is made up of a rounded, almost botryoidal cluster of acicular, radiating Ramsdellite crystals. They are very small, not exceeding 3 mm in length, and appear to be in generally good condition, with little human-induced damage. The crystals have a black color and a submetallic luster, and are coated in some areas with a very thin layer of a brownish, muddy-looking material. Such a piece would probably best be displayed in a lidded specimen box, as it would supply the most protection to the thin needles.
no photo
ram-1 ($ 22.00)
Mistake Mine, Yavapai County, Arizona, U.S.A.
RAMSDELLITE specimen ram-2
$ 30.00
Dims: 1.3" x 1.0" x 0.8" (3.3 x 2.5 x 2.0 cm)
Wt: 20.2 g
Mistake Mine, Yavapai County, Arizona, U.S.A.
The base rock of this particular specimen appears to be made up of goethite, as it has the proper brown coloration, but it is not powdery and messy like goethite often is, and it has a faint sparkly sheen that indicates that it is coated with some form of microscopic crystals. Coating part of this host rock is a thick, almost botryoidal layer of acicular, radiating Ramsdellite crystals. These crystals appear to be in excellent condition, with no apparent human-induced damage. They have reasonably good form, looking like small spikes that radiate out of the base. None of these crystals exceeds 3 mm in length, and all have a dark gray color and a metallic luster. They remind me strongly of pyrolusite.
no photo
ram-2 ($ 30.00)
Mistake Mine, Yavapai County, Arizona, U.S.A.
RAMSDELLITE specimen ram-3
$ 60.00
Dims: 2.0" x 1.3" x 0.9" (5.1 x 3.3 x 2.3 cm)
Wt: 22.1 g
Mistake Mine, Yavapai County, Arizona, U.S.A.
The Ramsdellite on this specimen consists of tiny acicular, mostly radiating crystals that form a crust over a somewhat fragmented flint base. The crystals do not exceed 3 mm in length and have a dark gray color and a metallic luster. They tend to radiate upwards, but there is a substantial area on the crust that is made up of what appear to be botryoidal clusters of crystals that run tangent to the clusters' rounded shapes- they remind me of geodesic domes! I have no idea what causes this formation, but I am pretty certain that it has something to do with one of the earlier-forming layers in the crust. There seems to be a small amount of damage to the crust, but it is difficult to tell if it is human-induced. It is quite a pretty piece, actually, and those weird "geodesic" formations are intriguing.
no photo
ram-3 ($ 60.00)
Mistake Mine, Yavapai County, Arizona, U.S.A.
RAMSDELLITE specimen ram-4
$ 80.00
Dims: 1.5" x 1.2" x 0.6" (3.8 x 3.0 x 1.5 cm)
Wt: 15.5 g
Lake County, New Mexico, U.S.A.
This small specimen consists of 2 intergrown sprays of orthorhombic Ramsdellite crystals. These crystals are the largest that I have seen for this mineral, topping off at 1.5" (3.8 cm) in length. Though their form is not easily definable, their crystalline shape is certainly easy to see and their faces and edges are visible, though somewhat uneven. They have a dark gray color and a dull metallic luster. Interestingly, the sprays radiate towards each other from almost perfectly opposite directions. There is a single crystal on the specimen that does not belong to either spray of crystals, as it has intersected a few crystals in a random direction. There is no host rock visible on the specimen, but there is an oddity that I should bring to light- on one of the longer crystals rest several tiny hexagonal prismatic crystals of an unknown mineral. They have excellent form and what appears to be a red-brown coloration. They appear to be transparent and have a vitreous luster. As their faces are not striated, I think that they could be apatites or possibly vanadinites.
no photo
ram-4 ($ 80.00)
Lake County, New Mexico, U.S.A.
RAMSDELLITE specimen ram-5
$ 42.00
Dims: 3.3 x 1.9 x 1.5" (8.4 x 4.8 x 3.8 cm)
Wt: 4.5 oz. (128.1 g)
Mistake Mine, Yavapai County, Arizona, U.S.A.
This hand specimen consists of a dull brown, porous host rock which is mostly enveloped by a thick layer of crystalline Ramsdellite. According to the documentaion, the Ramsdellite has at least partly psueduomorphed into pyrolusite, but for the sake of simplicity I will consider it Ramsdellite. The crystals that make up the crust do not exceed more than 0.3" (8 mm) in any dimension, but are generally in excellent condition, as damage is limited to those crystals that line the edges of the crust. All have a good orthorhombic prismatic form though they are heavily intergrown; their edges are reasonably well-defined and their edges are moderately smooth and clean, possessing a submetallic luster that is almost silky in appearance. Their color is a basic gray-black and all are thoroughly opaque.
no photo
ram-5 ($ 42.00)
Mistake Mine, Yavapai County, Arizona, U.S.A.
RAMSDELLITE specimen ram-6
$ 75.00
Dims: 3.5 x 2.2 x 1.5" (8.9 x 5.6 x 3.8 cm)
Wt: 6.3 oz. (179.6 g)
Mistake Mine, Yavapai County, Arizona, U.S.A.
This hand specimen is mostly Ramsdellite by weight, though a substantial portion of it has pseudomorphed into Pyrolusite. It occurs as a cluster of heavily-intergrown orthorhombic prismatic crystals that do not exceed 0.5" (1.3 cm) in length and are generally in very good condition- damage appears to be confined to a few very exposed areas. Their form is fairly good, as their intergrowth provides much interference; the crystals tend to have moderately well-defined edges and curved and slightly disseminated faces that possess a dull metallic luster. The small amount of host rock that is present on the specimen has a moderately dark brown color, a thoroughly dull luster, and is quite porous in nature.
no photo
ram-6 ($ 75.00)
Mistake Mine, Yavapai County, Arizona, U.S.A.
RAMSDELLITE specimen ram-7
$ 27.00
Dims: 2.2 x 2.0 x 0.8" (5.6 x 5.1 x 2.0 cm)
Wt: 2.06 oz. (58.5 g)
Mistake Mine, Yavapai County, Arizona, U.S.A.
This small hand specimen consists of a few intersecting crusts of crystalline Ramsdellite. Each crust is made up of dozens of heavily-intergrown Ramsdellite crystals that do not exceed 0.3" (8 mm) in any dimension. All are in reasonably good condition- there is little damage present- and have good monoclinic prismatic form, given to their intense intergrowth. They are colored a dark gray-black and have a dull metallic luster. Only a small amount of a dull brown host rock is present.
no photo
ram-7 ($ 27.00)
Mistake Mine, Yavapai County, Arizona, U.S.A.
RAMSDELLITE specimen ram-8
$ 25.00
Dims: 2.2 x 1.7 x 1.5" (5.6 x 4.3 x 3.8 cm)
Wt: 3.68 oz. (104.5 g)
Mistake Mine, Yavapai County, Arizona, U.S.A.
A crust of heavily-intergrown Ramsdellite crystals partly coats the sparse brown host rock of this piece. These crystals reach dimensions of 0.3 x 0.2 x 0.1 (9 x 5 x 3 mm) and are generally in fair-to-good condition, as much damage is visible. Even with their intense intergrowth, their orthorhombic prismatic form is quite good, with relatively well-defined edges and clean faces. All have a dark gray-black coloration and a slightly dull metallic luster, and tend to have a powdery coating that wears off easily. The host rock on which they rest strongly resembles volcanic rock, as it is hard and quite porous.
no photo
ram-8 ($ 25.00)
Mistake Mine, Yavapai County, Arizona, U.S.A.
RAMSDELLITE specimen ram-9
$ 58.00
Dims: 3.2 x 2.8 x 2.4" (8.1 x 7.1 x 6.1 cm) .... Wt: 11.9 oz. (336.0 g) .... Loc: Mistake Mine, Yavapai County, Arizona, U.S.A
This hand specimen consists of a dull brown, porous host rock whose top is covered with crystalline Ramsdellite. Thre are dozens of orthorhombic prismatic crystals 3 or 4 mm in length, and in very good condition. A thick layer of Ramsdellite showing a boytroidal form with radiating acicular crystals provides the base upon which the orthorhombic crystals have grown.
no photo
ram-9 ($ 58.00)
RAMSDELLITE specimen ram-10
$ 25.00
Dims: 3.0x2.2x1.0" (7.5x5.5x2.5cm)
Wt: 3.57 oz. (101g)
Mistake Mine, Yavapai County, Arizona, U.S.A.
This is a chunk of granular ramsdellite. It shows no hint of crystal form, except under a loupe which reveals that there are thousands of crystals, some up to a millimeter in length, that are embedded in the mass of still smaller crystals. The specimen has a rather unusual appearance, due to the slightly dull reflections from thousands of crystal faces. A thin coating of light brown host rock remains on one face of the specimen.
no photo
ram-10 ($ 25.00)
Mistake Mine, Yavapai County, Arizona, U.S.A.


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