Strontiohurlbutite

Chemical formula: SrBe₂(PO₄)₂

Strontiohurlbutite is a rare beryllium strontium phosphate, forming colorless or white tabular crystals, and is the strontium analogue of hurlbutite.

## Characteristics Strontiohurlbutite is a rare mineral from the phosphate group, chemically classified as a beryllium strontium phosphate. It is the strontium analogue of the more well-known hurlbutite, in which calcium is replaced by strontium. It occurs as small, well-formed crystals with a tabular or short prismatic habit, reaching sizes of up to several millimeters. Most often, it forms colorless or white, transparent crystals with a strong, vitreous luster. Due to its rarity and small crystal size, it is a mineral primarily of scientific and collecting interest. ## Physical Properties This mineral is characterized by high hardness, measuring 8 on the Mohs scale, a value similar to topaz. Its luster is intensely vitreous. It is a transparent mineral. The density calculated based on the formula and unit cell parameters is approximately 3.86 g/cm³. ## History and Name The mineral's name refers to its chemical composition – the dominance of strontium (strontio-) and its structural similarity to the mineral hurlbutite (-hurlbutite). Hurlbutite, in turn, was named after Cornelius Searle Hurlbut Jr. (1906-2005), a professor of mineralogy at Harvard University. Strontiohurlbutite was approved as a new mineral by the International Mineralogical Association (IMA) in 1997. ## Applications Strontiohurlbutite has no industrial applications. Its significance is limited to scientific research in the field of systematic mineralogy and crystal chemistry, and to advanced collections specializing in rare minerals or pegmatite minerals.

Properties

Mohs hardness: 8
Luster: Vitreous
Streak: White
Density: 3.86
Cleavage: Indistinct
Fracture: Uneven to conchoidal
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Identifying strontiohurlbutite in the field is practically impossible without specialized equipment. In a collection, identification is based on the characteristic crystal form (short, tabular), very high hardness (8 on the Mohs scale), vitreous luster, and most importantly, confirmed provenance from one of the known localities. Final identification requires advanced analytical methods, such as Raman spectroscopy or EDS analysis, to confirm the chemical composition (presence of strontium, beryllium, and the phosphate group). ## Distinguishing from Similar Minerals Strontiohurlbutite can be confused with other colorless pegmatite minerals, such as hurlbutite, herderite, beryllonite, or quartz. It is distinguished from hurlbutite by the dominance of strontium over calcium, which cannot be determined without chemical analysis. It is significantly harder than quartz and herderite. Beryllonite has lower hardness (5.5-6) and perfect cleavage. ## Crystal Forms Strontiohurlbutite crystals are small, usually not exceeding 2 mm. They adopt a tabular form, flattened along the {010} plane, or short prismatic. They crystallize in the monoclinic system.

Geological environment

## Genesis Strontiohurlbutite is a mineral of hydrothermal origin, associated with granitic pegmatites. It forms in the late stages of pegmatite crystallization, in vugs and fractures, as a result of the interaction of phosphorus-rich solutions with beryllium-bearing minerals. The presence of strontium in the crystallization environment is a key factor determining its formation. ## Mineral Associations This mineral co-occurs with other minerals typical of granitic pegmatites. In the type locality (Linópolis, Brazil), it was found in association with quartz, albite, microcline, muscovite, beryl, columbite-(Mn), hydroxylherderite, wardite, eosphorite, and brazilianite. ## Localities The most important and type locality for strontiohurlbutite is the Córrego Frio mine, located near Linópolis, in the municipality of Divino das Laranjeiras, Minas Gerais state, Brazil. This is so far the only confirmed and well-documented locality for this mineral worldwide.

Rarity

Very rare

For collectors

## Quality Criteria The most highly prized strontiohurlbutite specimens are those with sharply terminated, well-formed, and transparent crystals, clearly standing out from the host rock (matrix). Due to the small size of the crystals, their quality and perfect form are crucial. Specimens with several crystals or in association with other rare phosphates (e.g., hydroxylherderite) are particularly desirable. Purity and lack of damage are absolutely key. ## Popular Localities The only source of collector specimens is the Córrego Frio mine in Minas Gerais, Brazil. All specimens available on the market come from this single locality, which makes them easy to identify by origin but also very rare.

Care and storage

## Cleaning Cleaning is recommended only with a soft brush to remove dust. Due to its high hardness, it is resistant to scratches, but aggressive mechanical methods that could damage delicate crystals or the host rock should be avoided. ## What to Avoid Avoid contact with strong acids, which can potentially damage the mineral's surface. Despite high hardness, brittle crystals can be damaged by impact or dropping. There are no specific recommendations regarding exposure to light or temperature changes. ## Storage Strontiohurlbutite specimens, due to their small size and scientific value, are best stored in sealed "micromount" boxes, which protect them from dust and mechanical damage. A label with the exact locality is crucial for the specimen's value.

Sources

IMA Mineral List (CNMNC)