THE MINERAL MOTTRAMITE

Dims: 2" x 1-3/4" x 1-1/8"

Wt: 1.31 oz

Total Wreck Mine, Pima Co., Arizona, U.S.A.

This specimen consists of a host rock that looks suspiciously like goethite, upon which are dozens of black, rectangular blades of Mottramite. These black blades are dusted with what appears to be microscopic crystals of more Mottramite, although I cannot really be certain. It makes me think of blades of black wulfenite covered with a tiny druse of goethite, or some other black mineral. The blades achieve a maximum length of about 3/16", and 1/8" width. I have recently been told by an illustrious and knowledgable rockhound by the name of Tim Jokela that this specimen is actually a pseudomorph after wulfenite; that makes a lot of sense, given the form that the Mottramite is in.

Dims: 3.9 x 3.2 x 2.0" (9.9 x 8.1 x 5.1 cm)

Wt: 1 lb., 0.5 oz. (467 g)

Tsumeb Mine, Tsumeb, Namibia

This specimen consists of dozens of arborescent Mottramite formations that are intergrown and partly embedded in a calcite base. Most of the formations are damaged or incomplete and their intergrowth makes them difficult to effectively measure, but where intact they seem to be well-formed. The formations branch off to form crystals that have well-defined edges and clean faces. All appear to have a dull olive-green coloration on their intact surfaces, whereas damaged surfaces show a darkgray color. Oddly enough, these damaged areas show a submetallic luster that is duller than that of the intact surfaces, which have a very bright pearly-to-vitreous shine. All are well embedded into the calcite base, which is made up of many intergrown trigonal crystals, most of which show at least slight damage.

Dims: 3.3 x 1.9 x 1.8" (8.3 x 4.9 x 4.6 cm)

Wt: 6.2 oz. (174 g)

Total Wreck Mine, Pima County, Arizona, U.S.A.

This interesting specimen consists of a Mottramite crust that almost completely covers a nondescript, gray base rock. Much of the crust is in the form of a sparkling druse of tiny crystals and a large area of tightly-arranged stalactitic formations. These formations are generally in very good condition- a few are obviously damaged- and reach lengths of 0.3" (8 mm). All have a black color and a bright, pearly luster. A portion of the specimen has also been coated with a layer of a massive, dark brown material that I cannot identify. Like other specimens that I have seen from this mine, the Mottramite might be a pseudomorph from another mineral.

Dims: 1.7 x 1.6 x 0.7" (4.2 x 1.1 x 1.9 cm)

Wt: 21 g

Total Wreck Mine, Pima County, Arizona, U.S.A.

This hand specimen consists of a crust of tiny Mottramite crystals that rests on what appears to be a base made up of a descloizite druse. These Mottramites are in good condition - some damage to the druse is visible - and all are microscopic in size. Thus, they are too small to effectively study even with a loupe. All are black in color and have a sparkling, vitreous luster. The black color is likely caused by inclusions of goethite or some other oxide. The crystals that serve as the base actually look more like hopeite than descloizite - I really cannot be sure what they are.

Dims:2.0x1.2x0.8" (5.1x3.0x2.0 cm)

Wt: 1.3oz. (38g)

Blanchard Mine, Socorro cty., New Mexico

This specimen consists of a druse of tiny quartz crystals coated with a green layer of mottramite. As the mottramite is only a very thin film, nothing can be told of its crystallography on this specimen. Black flecks in the matrix of this piece are biotite mica.

Dims:1.2x1.2x1.0" (3.0x3.0x2.5 cm)

Wt: 0.8oz. (24g)w/base

Tsumeb mine, Tsumeb, Namibia

The matrix of this specimen is covered with nodules of fuzzy green mottramite. The mottramite gives this specimen a velvet-like appearance. No individual crystals of mottramite are visible. The back of the specimen is coated with hundreds of tiny rhombohedrons of calcite. This specimen is attached to a clear acrylic base.

Dims:2.4x1.9x1.7" (6.1x4.8x4.3 cm)

Wt: 3.5oz. (98g)

Blanchard Mine, Hansonburg Mining District, Socorro cty., New Mexico

The top surface of this specimen is covered with drusy quartz. This quartz is in turn covered with a thin coating of greenish-yellow mottramite. No crystals of this mineral are visible, even with a loupe. There is a small amount of crystalline galena on one edge of the mottramite occurence. There is only minor damage to this specimen.

Dims:3.4x2.9x1.6" (8.6x7.4x4.1 cm)

Wt: 16.5oz. (467g)

Tsumeb Mine, Tsumeb, Namibia

Large, dendritic sprays of mottramite crystals cover the face of a calcite matrix in this specimen. Individual crystals reach 0.2" (0.5cm) in length, but the sprays of crystals range up to 0.7" (1.8cm). Damage on this specimen is mostly confined to the edges of the specimen, where it was broken from the host rock. Some of the calcites show damage-one on the display side, the rest on the back of the piece. This is one of the better mottramites that I have seen, in cabinet size.

Dims: 0.98x0.50x0.27" (2.48x1.28x0.68cm)

Wt: 0.09oz (2.6g)

Thunderbird Mine, Pinal County, Arizona, USA

The bright, sparkly crystals here are composed of rounded clusters of thin sheets of motramite crystals, but except for the sparkly, all of these details are too small to be seen without a loupe. The motramite appears to have formed (in places) on top of brown vanadinite crystals.

Dims: 3.27x1.63x0.95" (8.30x4.15x2.42cm)

Wt: 2.51oz (71.2g)

Chance Mine, Mono County, California, USA

A piece of quartz sports a crust of pale yellow-green mottramite, which shades into a crust of light brown dewcloizite. These are end members of the descloizite series, with the copper rich end member being mottramite. The mottramite appears to be a dull crust, but a loupe resolves thousands of tiny dull green balls that grade smoothly into the (identically formed) light brown descloizite.