Augelite

Chemical formula: Al₂PO₄(OH)₃

Augelite is a rare aluminum phosphate, valued by collectors for its well-formed, vitreous, and often colorless crystals.

## Characteristics Augelite is a hydrated aluminum phosphate, most commonly forming tabular or prismatic crystals. It usually occurs as single, well-formed crystals or their radial aggregates. Its name comes from the Greek word *auge* meaning "luster" or "brilliance," which directly refers to its characteristic, strong vitreous luster. Specimens are typically colorless or white, although they can take on delicate shades of yellow, green, and even rare blue or pink. ## Physical Properties This mineral is characterized by a hardness in the range of 4.5-5 on the Mohs scale, making it relatively brittle. It has a density of approximately 2.7 g/cm³. Its most distinctive feature is a strong, vitreous luster on crystal faces and fracture surfaces. It is transparent, which, combined with its luster, gives it an appearance resembling glass or some varieties of topaz. ## Colors and Varieties The predominant color of augelite is its absence – colorless and white crystals are most commonly found. Less common are specimens with delicate coloration, such as pale yellow, light green, and exceptionally rare blue or pink. There are no named color varieties or commercial names. ## History and Name Augelite was first described in 1868 by Christian Wilhelm Blom, who identified it in material from the Västanå (Westanå) iron mine in the Skåne region of Sweden. The name, given by Blom, comes from the Greek word *αὐγή* (auge), which means "brilliance" or "luster," accurately describing the mineral's appearance. ## Uses Augelite has no industrial applications. It is a mineral of purely scientific and collector's interest, sought after due to its rarity and the aesthetics of its well-formed crystals.

Properties

Mohs hardness: 4.5-5
Luster: Vitreous
Streak: White
Density: 2.696
Cleavage: Perfect on {110}, <mi>good on {_201}, imperfect on {001} and {_101}</mi>
Fracture: Irregular/Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Augelite can be identified by its characteristic, very strong vitreous luster, transparency, and crystal habit – often tabular or thick, prismatic. Excellent cleavage in one direction is also an important diagnostic feature, visible on some specimens as flat, shiny fractures. Occurrence in paragenesis with other phosphates, such as lazulite, is an additional clue. ## Distinguishing from Similar Minerals Augelite is sometimes confused with colorless quartz, topaz, barite, or anglesite. It differs from quartz by its lower hardness (quartz has a hardness of 7) and excellent cleavage (quartz does not have cleavage). It also differs from topaz by its lower hardness. Compared to barite and anglesite, augelite is significantly lighter (has a lower density). ## Crystal Forms It crystallizes in the monoclinic system, forming thick, tabular crystals, often with a rhombic cross-section, as well as short prismatic or columnar forms. Crystals can occur individually or form fan-shaped and radial aggregates. It is less commonly found in granular aggregates or massive forms.

Geological environment

## Genesis Augelite is a mineral of hydrothermal or metamorphic origin. It forms in hydrothermal veins rich in phosphorus and aluminum, cutting through metamorphic rocks such as quartzite. It can also form as a result of the metamorphism of phosphate- and aluminum-rich sediments. It is also found in some granitic pegmatites. ## Mineral Associations This mineral often co-occurs with other phosphates. Its typical associated minerals include lazulite, attakolite, svanbergite, trolleite, pyrite, hematite, barite, and quartz. ## Localities The most important and historical locality is the Västanå mine in Sweden. High-quality, transparent crystals come from the White Mountain area in California (USA), where they occur in paragenesis with lazulite. Other known localities include the Potosí Province in Bolivia, the Rapid Creek mine in Yukon Territory, Canada, as well as sites in Austria, Rwanda, and Peru.

Rarity

Rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with sharply terminated, fully transparent, and lustrous crystals, free from mechanical damage. Crystals of significant size (above 1-2 cm), especially those embedded in a contrasting rock matrix, are highly prized. Specimens from rare localities or with unusual coloration (greenish, blue) also fetch a higher value. Aesthetic compositions, such as radial aggregates, are particularly sought after. ## Popular Localities Among the most desirable on the collector's market are specimens from White Mountain in California, USA, which are famous for their large, vitreous, and often colorless crystals. Classic, though less readily available, are specimens from the type locality in Sweden. Crystals from Bolivia and Canada (Yukon) are also very popular.

Care and storage

## Cleaning Augelite crystals are sensitive to chemicals and mechanical damage. For cleaning, use only distilled water and a very soft brush. Avoid ultrasonic cleaners, which can cause cracks along cleavage planes. ## What to Avoid Avoid contact with acids and other chemicals. Due to its relatively low hardness, augelite is susceptible to scratches, so it should not come into contact with harder minerals. Protect it from sudden temperature changes and impacts. ## Storage Augelite specimens are best stored in separate, padded boxes or on a soft surface in display cases, away from harder minerals. Protect from dust and direct, prolonged sunlight, although it is not particularly light-sensitive.