Gorerite

Chemical formula: CaAlFe³⁺₁₁O₁₉

Goreyite is a rare calcium, aluminum, and iron oxide, related to hibonite, occurring as microscopic inclusions in metamorphic rocks.

## Characteristics Goreyite is an oxide mineral belonging to the magnetoplumbite supergroup. It is the iron (Fe³⁺) analogue of hibonite. It occurs as hexagonal, platy crystals not exceeding 200 micrometers in size, typically as inclusions within other minerals, mainly corundum. Due to its microscopic size, its visual features are difficult to observe without specialized equipment. ## Physical Properties Goreyite crystals exhibit a metallic to submetallic luster. Hardness and density have not been precisely measured due to the small size of the samples, but based on VHN hardness (1300), it can be estimated at approximately 7.5-8 on the Mohs scale. It is a brittle mineral. ## Colors and Varieties Observed crystals are black and leave a reddish-brown streak. No varieties of this mineral have been distinguished. ## History and Name The name goreyite comes from its discovery locality – the Hatrurim Formation in Israel, known locally as the "Burnt Rock" (in Hebrew "ha-Gorer"). The mineral was approved by the International Mineralogical Association (IMA) in 2021, and its description was published in 2022. The authors of the description are V. V. Sharygin, S. N. Britvin, M. N. Murashko, and R. K. Vapnik.

Properties

Mohs hardness
5-6
Color
black
Luster
Metallic
Streak
black, occasionally displaying a brown tint
Density
5.36
Cleavage
good on (001)
Fracture
Irregular/Uneven
Transparency
Opaque
Crystal system
Hexagonal

Diagnostic features

## Identification Identification of goreyite is only possible using advanced analytical methods, such as scanning electron microscopy (SEM) with chemical composition analysis (EDS) and electron backscatter diffraction (EBSD). In reflected light, it is opaque, gray with a slight brownish tint, and exhibits weak pleochroism. ## Distinguishing from Similar Minerals Hibonite, its aluminum analogue, is practically impossible to distinguish without chemical analysis. Other dark, opaque minerals from the magnetoplumbite group, such as magnetite or hematite, also require specialized examination for unambiguous differentiation when occurring on such a small scale. ## Crystal Forms Goreyite forms hexagonal, platy or tabular crystals, which typically occur as single, isolated inclusions within larger corundum crystals.

Geological environment

## Genesis Goreyite forms under pyrometamorphic conditions at high temperatures. It was discovered in rocks of the Hatrurim Formation, which underwent combustion as a result of natural ignition and prolonged burning of bitumens contained in the host rocks (marls). ## Mineral Associations This mineral co-occurs directly with corundum (as inclusions), hematite, grossular, hibschite-katoite, calcite, cancrinite, tobermorite, afwillite, and hydrocalumite. ## Localities The only confirmed locality for goreyite worldwide is its type locality: the Nabi Musa deposit within the Hatrurim Formation, in the Judean Desert, Israel.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, goreyite is not traded on the collector's market as isolated specimens. Only samples of the host rock from the type locality, containing well-documented and analytically studied microcrystals, have collector value. Specimens with the largest (on a micro scale) and clearest goreyite crystals within the accompanying corundum are most highly prized.

Care and storage

## Cleaning Due to its microscopic size and occurrence as inclusions, individual goreyite crystals are not subject to cleaning. Specimens of the host rock can be cleaned mechanically, using a soft brush and distilled water. ## What to Avoid Contact with strong acids, which could potentially damage the mineral, should be avoided. There is no detailed data on sensitivity to light or temperature, but standard caution is recommended as with other rare minerals. ## Storage Specimens containing goreyite should be stored in stable conditions, away from dust and chemical contaminants. It is best to keep them in sealed collector boxes or display cabinets.

External references

Sources

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