Svanbergite

Chemical formula: SrAl<sub>3</sub>(S<sup>6+</sup>O<sub>4</sub>)(PO<sub>4</sub>)(OH)<sub>6</sub>

Svanbergite is a rare mineral from the alunite group, a strontium-aluminum sulfate-phosphate, valued for its well-formed, vitreous crystals.

## Characteristics Svanbergite is a complex strontium-aluminum sulfate-phosphate belonging to the alunite supergroup. It forms trigonal crystals, often pseudo-orthorhombic or pseudocubic, which can be tabular or rhombohedral. It typically occurs as small but well-formed crystals, grown on or within the host rock. Specimens are most often opaque to translucent, with a vitreous or slightly resinous luster. ## Physical Properties This mineral is characterized by a Mohs hardness of approximately 5, making it relatively hard but susceptible to scratching by harder minerals. Its density ranges from 3.2 to 3.3 g/cm³. Crystals exhibit distinct cleavage in one direction, and their fracture is most often uneven or conchoidal. ## Colors and Varieties Svanbergite occurs in various colors, most commonly in shades of yellow, brown, reddish, and pink. Colorless, white, gray, and even greenish crystals are also found. No named varieties are distinguished, and color variation depends on impurities and crystallization conditions. ## History and Name The mineral's name, given in 1854 by Lars Fredrik Svanberg, honors himself. Svanberg was a Swedish chemist and mineralogist who first studied and described this mineral. The type locality, from which the first described specimens originated, is the Hållsjöberg mine in the Värmland region of Sweden. ## Uses Svanbergite has no industrial significance. Its only use is as an object of interest for collectors of rare minerals and a subject of scientific research due to its complex structure and chemical composition.

Properties

Mohs hardness
5
Luster
Vitreous to resinous
Streak
White
Density
3.2 - 3.3
Cleavage
Distinct/Good on {0001}
Fracture
Conchoidal to uneven
Transparency
Transparent to translucent
Crystal system
Trigonal

Diagnostic features

## Identification Svanbergite is most easily recognized by its characteristic crystal shape – often rhombohedra or pseudocubes with trigonal symmetry. Vitreous luster, relatively high hardness (approx. 5), and occurrence in specific geological environments (e.g., aluminum and phosphorus-rich deposits) are key diagnostic features. ## Distinguishing from Similar Minerals It can be confused with other minerals from the alunite supergroup, such as woodhouseite or hinsdalite, from which differentiation often requires advanced chemical analyses (EDS/XRD) to confirm the dominance of strontium, sulfates, and phosphates. Visually, it can resemble some garnets or feldspars, but differs from them in hardness, crystal shape, and environment of occurrence. ## Crystal Forms Svanbergite crystals are usually small, rhombohedral in habit, often flattened or tabular. Sometimes they form cube-like (pseudocubic) shapes. They occur as single, well-formed crystals grown on the host rock or as granular and massive aggregates.

Geological environment

## Genesis Svanbergite is a secondary mineral or a product of hydrothermal and metamorphic processes. It forms in aluminum-rich rocks that have been subjected to solutions containing phosphates and sulfates. It often forms in hydrothermal alteration zones of ore deposits, in phosphate-rich sedimentary rocks, and in some metamorphic rocks, such as andalusite schists. ## Mineral Associations It often co-occurs with minerals such as pyrophyllite, diaspore, andalusite, lazulite, augelite, barite, quartz, and also with other members of the alunite supergroup, e.g., woodhouseite and hinsdalite. ## Localities The most important and historical localities for svanbergite are in Sweden (Hållsjöberg, Värmland – type locality). Significant specimens also come from the Champion Mine in the White Mountains, California (USA), where it was found in association with lazulite and augelite. Other known localities include Bolivia, Australia, and some Alpine localities in Switzerland and Austria.

Rarity

Rare

For collectors

## Quality Criteria The most prized by collectors are specimens with sharply defined, well-formed crystals of intense color (e.g., pink, red, honey-yellow) and good luster. Contrast with the rock matrix on which the crystals are embedded is important. Large, undamaged crystals, especially those with high transparency, are rare and command significantly higher prices. Aesthetic associations with other minerals, such as lazulite, also enhance their appeal. ## Popular Localities Specimens from the classic locality of Champion Mine in California (USA) are considered among the best in the world and set the standard for quality for this mineral. Historical specimens from Sweden are also sought after by collectors specializing in minerals from type localities.

Care and storage

## Cleaning Svanbergite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. After wet cleaning, the specimen should be thoroughly dried. ## What to Avoid The mineral is sensitive to strong acids, which can damage it. Contact with household and laboratory chemicals should be avoided. It should also not be subjected to ultrasonic or steam cleaning. Prolonged exposure to intense sunlight can cause some colored specimens to fade. ## Storage Svanbergite is best stored in individual, padded boxes or display cases to prevent scratching by harder minerals. Due to its brittleness, it should be protected from impacts and falls. It is good to keep it in stable conditions, away from sources of moisture and sudden temperature changes.

External references

Sources

Read more