Bartelkeite is an exceptionally rare mineral, one of scarce natural

germanium Germanium is a chemical element; it has Symbol (chemistry), symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid or a nonmetal in the carbon group that is chemically ...

compounds. The formula was originally assumed to be PbFeGe₃O₈,Keller, V.P., Hess, H., and Dunn, P.J., 1981. Bartelkeit, PbFe²⁺Ge₃O₈, ein neues Germanium-Mineral von Tsumeb, Namibia. Chemie der Erde 40, 201-206 (in German) bartelkeite was later shown to be isostructural with a high-pressure form of the mineral

lawsonite Lawsonite is a hydrous calcium aluminium sorosilicate mineral with formula CaAl2Si2O7(OH)2·H2O. Lawsonite crystallizes in the orthorhombic system in prismatic, often tabular crystals. Crystal twinning is common. It forms transparent to transluce ...

. Thus, its correct formula is PbFeGe(Ge₂O₇)(OH)₂•H₂O.Origlieri, M.J., Yang, H., Downs, R.T., Posner, E.S., Domanik, K.J., and Pinch, W.P., 2012. The crystal structure of bartelkeite, with a revised chemical formula, PbFeGe^VI(Ge₂^IVO₇)(OH)₂·H₂O, isotypic with high-pressure ''P''2₁/''m'' lawsonite. American Mineralogist 97(10), 1812-1815 Bartelkeite and mathewrogersite are minerals with essential (dominant)

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

and

. Both come from

Tsumeb Tsumeb (; ) is a city of around 35,000 inhabitants and the largest town in the Oshikoto Region, Oshikoto region in northern Namibia. Tsumeb, since its founding in 1905, has been primarily a mining town. The town is the site of a deep mine (the ...

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

- a world's "capital" of germanium minerals.

Occurrence and association

Bartelkeite was detected in voids of

ore occurring within dolomites. The mineral associates with

galena Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals. It crysta ...

germanite Germanite is a rare copper iron germanium sulfide mineral, Cu26Fe4Ge4S32. It was first discovered in 1922, and named for its germanium content. It is only a minor source of this important semiconductor element, which is mainly derived from the p ...

reniérite Renierite is a rare copper zinc germanium bearing sulfide mineral with the chemical formula . It occurs at the Kipushi Mine, Democratic Republic of the Congo; and Namibia Namibia, officially the Republic of Namibia, is a country on the we ...

, and

tennantite Tennantite is a copper arsenic sulfosalt mineral with an ideal formula . Due to variable substitution of the copper by iron and zinc the formula is . It is gray-black, steel-gray, iron-gray or black in color. A closely related mineral, tetrahed ...

Crystal structure

Bartelkeite is the first analyzed mineral containing both tetrahedrally- and octahedrally-coordinated germanium. It is isostructural with high-pressure form of the silicate

. In the structure there are: * chains of FeO₆ and GeO₆ octahedra, that share edges * Ge₂O₇ dimers that cross-link the chains * Pb atoms and water molecules in large cavities of the framework

References

Oxide minerals Germanium minerals Lead minerals Iron(II) minerals Monoclinic minerals Minerals in space group 4 Minerals in space group 11 Minerals described in 1981 {{mineral-stub