Gottlobite
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| Gottlobite | |
|---|---|
| General | |
| Category | Hydroxide mineral |
| Formula (repeating unit) | CaMg(VO4, AsO4)(OH) |
| Strunz classification | 08.BH.35 |
| Dana classification | 41.05.01.10 |
| Crystal system | Orthorhombic |
| Space group | P222 |
| Unit cell | a = 7.501(4) Å; b = 9.010(7) Å; c = 5.941(4) Å; Z = 4, V = 401.5Å3 |
| Identification | |
| Formula mass | 205.20 gm |
| Color | Orange to orange-brown |
| Crystal habit | Isometric to tabular crystals |
| Twinning | Not observed |
| Cleavage | Not observed |
| Fracture | Conchoidal to irregular |
| Tenacity | Brittle |
| Mohs scale hardness | 4.5 |
| Luster | Vitreous to adamantine |
| Streak | Light brownish |
| Diaphaneity | Transparent |
| Specific gravity | 3.46 g/cm3 (calculated) |
| Optical properties | Biaxial negative |
| Refractive index | nα = 1.797 nβ = 1.805-1.815 nγ = 1.828 |
| Pleochroism | Medium strong with X = orange-brown, Y = pale yellowish brown, and Z = orange-brown |
| References | [1]Cite error: A <ref> tag is missing the closing </ref> (see the help page). |
Gottlobite CaMg(VO4,AsO4)(OH) is a mineral found as isolated crystals or isometric grains of orange or orange-brown color. The maximum size of the crystals are a half millimeter and are part of the orthorhombic crystal system. Gottlobite is isostructural with adelite and is part of the vanadates and arsenates group. With these characteristics, it is similar to the minerals tangeite and austinite by x-ray diffraction methods. [2]
Occurrence
Gottlobite is a relatively rare mineral where only a small quantity of the mineral has been found. It was first observed at the site of a long-abandoned mine on the northern slope of Gottlob hill in Friedrichroda, Thuringia, Germany by Jὒrgen Graf. In this mine, Gottlobite is found in hydrothermal veins of barite that are cutting through conglomerate. The crystals of gottlobite can be found embedded in these barite veins or as stand-alone crystals on surrounding minerals. The associated minerals in the area are hausmannite, barite, vanadian adelite, and muscovite. [2]
Chemical and crystal properties
Analytical methods used on gottlobite to determine its chemical qualities include energy-dispersive x-ray spectrometry (EDX) and wavelength-dispersive x-ray spectrometry (WDX). The EDX revealed the presence and quantities of elements present in the mineral, including Ca, V, As, O and small amounts of Sr. Mg is in gottlobite's chemical formula, but was not found in the EDX testing because of the very similar arsenic (As) lines that were overlapping with magnesium (Mg). It was also determined that the arsenic (As) and vanadium (V) atoms are in tetrahedral coordination with oxygen (O), and the magnesium (Mg) atoms are in octahedral coordination. [2]