Haggertyite

Chemical formula: BaMgFe₂+₄Fe₃+₂Ti₄+₅O₁₉

Haggertyite is a rare, black mineral from the hollandite group, found in lamproitic volcanic rocks.

## Characteristics Haggertyite is a rare beryllium, magnesium, iron, and titanium oxide, belonging to the hollandite supergroup. It occurs as very small, hexagonal crystals with a tabular habit, usually not exceeding 100 micrometers in size. It is most commonly observed as inclusions in other minerals, such as phlogopite or richterite. Its color is black, and on fresh surfaces, it exhibits a metallic luster. ## Physical Properties Due to the extremely small size of its crystals, many of haggertyite's physical properties have not been fully determined. The mineral is opaque. Its hardness and density have not been precisely measured, but based on its chemical composition, the density is estimated to be approximately 4.92 g/cm³. ## Colors and Varieties This mineral is uniform in color – it occurs exclusively in black. No color varieties or commercial varieties are known. ## History and Name The name haggertyite honors Stephen E. Haggerty (born 1938), a professor and geologist at Florida International University, for his significant contributions to the study of oxide minerals in the Earth's mantle. The mineral was discovered in Crater of Diamonds State Park in Pike County, Arkansas, USA, and its description was approved by the International Mineralogical Association (IMA) in 1996. ## Uses Due to its rarity and microscopic size, haggertyite has no commercial or industrial applications. It is of purely scientific interest and is an object of interest for collectors specializing in rare minerals or minerals from specific localities.

Properties

Mohs hardness: 5-6
Luster: Metallic
Streak: Black
Density: 4.92
Cleavage: None
Fracture: Conchoidal
Transparency: Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Identification of haggertyite is practically only possible using advanced laboratory methods, such as X-ray microanalysis (EDS/WDS) combined with scanning electron microscopy (SEM) or X-ray diffraction (XRD). Under collector conditions, identification is impossible – it relies on trusting the label from a reputable source that has performed the analyses. ## Distinguishing from Similar Minerals It can be confused with many other black, opaque oxide minerals, such as ilmenite, magnetite, chromite, or other minerals from the hollandite group. Differentiation requires chemical composition analysis, especially to confirm the presence of barium, magnesium, and high titanium content. ## Crystal Forms Haggertyite forms very small, hexagonal crystals with a tabular habit. They usually occur as single, dispersed inclusions in the host rock or within crystals of other minerals.

Geological environment

## Genesis Haggertyite is a mineral of magmatic origin. It forms as an accessory phase in the early stage of crystallization from lamproitic magmas, which are rich in potassium and titanium, and poor in silica. It crystallizes under high pressure and temperature conditions, characteristic of the Earth's upper mantle. ## Mineral Associations This mineral occurs in association with minerals typical of lamproitic rocks. It most commonly coexists with phlogopite, richterite (potassic variety), enstatite, olivine, apatite, chromite, priderite, and spinel. It is often found as inclusions within phlogopite crystals. ## Localities The most important and type locality (località typica) is Prairie Creek, a volcanic pipe within Crater of Diamonds State Park in Pike County, Arkansas, USA. This is the only confirmed and well-documented locality for this mineral worldwide.

Rarity

Very rare

For collectors

## Quality Criteria The collector's value of haggertyite is not based on aesthetics, as its crystals are microscopic. Key criteria include: - **Analytical Confirmation:** The specimen must have its chemical composition confirmed by laboratory methods. Without analysis, it is merely a rock fragment. - **Richness:** The more haggertyite microcrystals on a given rock fragment, the better. - **Association:** Specimens showing haggertyite in association with well-formed crystals of other lamproitic minerals, e.g., as inclusions in phlogopite, are attractive. - **Locality:** The only desirable locality is the type locality – Crater of Diamonds in Arkansas. ## Market Prices Specimens are very rarely available on the market. Prices for small rock fragments with analytically confirmed haggertyite can range from tens to several hundred dollars, depending on the richness and quality of the specimen and the reputation of the seller.

Care and storage

## Cleaning Specimens containing haggertyite, which are typically fragments of the host rock, can be cleaned with a soft, dry brush to remove dust. Due to the microscopic size of the crystals, aggressive mechanical methods should be avoided. The use of distilled water is permissible, but ensure that the host rock is water-resistant. ## What to Avoid Avoid contact with strong acids and chemicals, which could damage not only haggertyite itself but primarily its associated minerals and the host rock. There is no detailed data on its sensitivity to light or temperature, but it is standard practice to avoid extreme conditions. ## Storage Specimens should be stored in stable, dry conditions, away from dust. It is best to store them in sealed perkyboxes, which protect them from mechanical damage and contamination. A label with precise locality information is crucial, as the scientific and collector value of the specimen is closely tied to it.

External references

https://en.wikipedia.org/wiki/https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FHaggertyite