Souzalite

Chemical formula: Mg<sub>3</sub>Al<sub>4</sub>(PO<sub>4</sub>)<sub>4</sub>(OH)<sub>6</sub>·2H<sub>2</sub>O

Souzalite is a rare magnesium and aluminum phosphate, forming small, acicular crystals with a characteristic blue-green color.

## Characteristics Souzalite is a hydrated magnesium and aluminum phosphate, belonging to the group of rare minerals. It typically occurs as small, elongated or acicular crystals, which can form radial or tangled aggregates. Its most characteristic feature is an intense blue-green or green-blue color. ## Physical Properties Souzalite crystals exhibit a vitreous luster. This mineral is translucent. Its Mohs hardness is approximately 5.5, and its density ranges between 3.05 and 3.11 g/cm³. ## Colors and Varieties Souzalite occurs in shades from green-blue to blue-green. No named varieties are distinguished. ## History and Name The mineral was named in honor of Luís de Souza, a Brazilian mining engineer and metallurgist. It was first described in 1949 based on samples from the Córrego Frio mine in Minas Gerais, Brazil. ## Uses Souzalite has no industrial applications. It is valued solely as a collector's mineral due to its rarity and attractive color.

Properties

Mohs hardness
5.5
Luster
Vitreous
Streak
White
Density
3.05-3.11
Cleavage
Good on {100}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Key diagnostic features of souzalite include its characteristic blue-green color, acicular or fibrous crystal habit, and occurrence in association with other phosphates in pegmatites. Vitreous luster and relatively low hardness are also helpful in identification. ## Distinguishing from Similar Minerals Souzalite is sometimes confused with other blue or green phosphates, such as lazulite or vivianite. It is usually distinguished from lazulite by its more acicular crystal habit (lazulite more often forms compact masses or granular aggregates). Vivianite is much softer (hardness 1.5-2) and often darkens upon exposure to light, turning indigo or almost black. ## Crystal Forms Souzalite crystallizes in the monoclinic system. It most often forms elongated, prismatic, or acicular crystals. It occurs as radial aggregates, tangled fibrous masses, or as individual crystals grown on the host rock.

Geological environment

## Genesis Souzalite is a secondary mineral, formed in hydrothermal zones or as a result of alterations in phosphorus-rich granitic pegmatites. It forms in rock fissures and cavities. ## Mineral Associations This mineral often co-occurs with other phosphates, such as lazulite, wardite, eosphorite, brazilianite, apatite, as well as with quartz, muscovite, and albite. ## Localities The most important locality, which is also the type locality, is the Córrego Frio mine in the municipality of Linópolis, Minas Gerais, Brazil. It is also known from the Rapid Creek area in Yukon Territory, Canada, where it occurs in siderite concretions. Other reported localities include Rwanda, among others.

Rarity

Very rare

For collectors

## Quality Criteria The most sought-after specimens by collectors are those with well-formed, distinct crystals of intense blue-green color. Rich radial or tangled aggregates, contrasting with a light host rock (matrix), are also highly valued. Crystal size is an important factor, as most are very small. ## Popular Localities Undoubtedly, the most prized specimens come from the type locality in Minas Gerais, Brazil, which yields the best-known crystals. Specimens from Yukon, Canada, are also sought after, although they often have a slightly different mode of occurrence.

Care and storage

## Cleaning Souzalite specimens should be cleaned very carefully, using a soft brush to remove dust. Brief rinsing in distilled water is permissible, followed by thorough drying. Ultrasonic cleaners should be avoided. ## What to Avoid The mineral is sensitive to acids and strong chemicals. It should be protected from high temperatures and prolonged exposure to direct sunlight, which can cause fading. ## Storage Souzalite is relatively brittle, so it is best stored in a separate, padded display box, away from harder minerals that could scratch it. Storage in humid conditions should be avoided.

Sources

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