Hashemite

Chemical formula: BaCr⁶⁺O₄

Hashemite is a very rare barium chromate with an intense yellow color, occurring as microscopic crystals.

## Characteristics Hashemite is a mineral from the chromate group, chemically corresponding to barium chromate. It occurs extremely rarely, forming very small, tabular or prismatic crystals, whose size usually does not exceed 0.2 mm. It is most often observed as aggregates or single, dispersed crystals grown on other minerals. Its most characteristic feature is its intense, lemon-yellow to orange-yellow color. ## Physical Properties Hashemite crystals exhibit a luster described as vitreous to greasy. They are transparent to translucent. The Mohs hardness is approximately 3. The density is relatively high, around 4.33 g/cm³. ## Colors and Varieties This mineral is monochromatic – it occurs in shades from lemon-yellow to orange-yellow. No color or commercial varieties are distinguished. ## History and Name The name hashemite comes from the Hashemite Kingdom of Jordan, where the mineral was discovered. It was first described by H. S. Sarp, B. W. D. Yardley, P. R. B. Schnetger, and V. A. D. G. de la Fuente in 1985, and its discovery took place in the Hatrurim Formation in Jordan. The International Mineralogical Association (IMA) approved it as a new mineral in 1984. ## Uses Hashemite has no industrial application. Its significance is purely scientific and collectible, and due to its extreme rarity and microscopic size, it is a coveted object for specialized collectors.

Properties

Mohs hardness: 3.5
Color: Brown, dark greenish brown, yellow-brown, yellow
Luster: Vitreous to greasy
Streak: Light yellow
Density: 4.54
Cleavage: Perfect {001} Good {010} {100}
Fracture: Uneven
Transparency: Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of hashemite under amateur conditions is practically impossible. It requires advanced analytical methods, such as Raman spectroscopy or chemical analysis using an electron microprobe (EDS/WDS). A preliminary indication may be its intense yellow color, high density, and co-occurrence with other rare minerals from the Hatrurim Formation. ## Distinguishing from Similar Minerals Hashemite should not be confused with other yellow secondary minerals. It is distinguished by its specific occurrence environment (pyrometamorphic rocks of the Hatrurim Formation) and unique chemical composition (barium chromate). Visually, it may resemble some microcrystalline uranium minerals, but it is not radioactive. ## Crystal Forms Hashemite forms very small, tabular crystals with a rhombic habit, often flattened. It occurs as single crystals, small groups of them, or dispersed aggregates on the surface of the host rock.

Geological environment

## Genesis Hashemite is a product of pyrometamorphism – a process of rock alteration under very high temperature but low pressure. It forms in carbonate rocks of the Hatrurim Formation (the so-called "Mottled Zone") that have undergone combustion due to the natural ignition of bitumens contained within them. It is a secondary mineral, crystallizing in voids and fractures of altered rocks. ## Mineral Associations This mineral co-occurs with other rare minerals typical of the Hatrurim Formation, such as bentorite, baryte, calcite, aragonite, gypsum, as well as minerals from the ettringite group and representatives of cementitious silicate phases (e.g., larnite, brownmillerite). ## Localities The only confirmed and classic locality for hashemite is the Hatrurim Formation in Jordan (type locality) and Israel. These are the only known locations in the world where this mineral can be found.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to the microscopic nature of hashemite, the main criterion for evaluating a specimen is the abundance and quality of crystals visible under magnification. Specimens with numerous, well-formed, and intensely colored crystals, clearly contrasting with the host rock, are most valued. The aesthetic composition and the presence of rare associated minerals are also important. ## Popular Localities The most highly prized specimens come from the type locality in the Hatrurim Formation in Jordan. Specimens from the Israeli part of this formation are equally valuable from a scientific and collecting perspective.

Care and storage

## Cleaning Specimens containing hashemite should be handled with the utmost care. Cleaning should be limited to gently removing dust with a soft brush or a photographic air blower. Do not use water or any chemical agents that could damage both the hashemite itself and associated minerals. ## What to Avoid Avoid contact with acids and other chemicals. The mineral is relatively soft, so it must be protected from scratching and impacts. It should not be subjected to ultrasonic cleaning. ## Storage Hashemite specimens, due to the microscopic size of their crystals, are best stored in specialized "micromount" boxes, which protect against dust and mechanical damage. Display should be away from sources of vibration and in stable temperature conditions.