Szaibélyite

Chemical formula: MgBO<sub>2</sub>(OH)

Szaibelyite is a basic magnesium borate, most commonly forming fibrous or chalk-white, felted aggregates resembling felt.

## Characteristics Szaibelyite is a mineral from the borate group, chemically a hydrated magnesium borate. It rarely forms well-developed, acicular or capillary crystals with a silky luster. Most often, it occurs as radial or tangled aggregates with a fibrous structure, resembling felt, asbestos, or glass wool. It is also found in the form of compact, earthy, or chalk-like masses, which are soft and light. ## Physical Properties This mineral is characterized by relatively low hardness, ranging from 3 to 3.5 on the Mohs scale, which means it can be scratched by a copper wire. Its density is also low, varying from 2.6 to 2.7 g/cm³. Crystals exhibit perfect cleavage in one direction. The luster in crystalline forms is silky, while in compact and earthy aggregates it becomes dull or earthy. ## Colors and Varieties Szaibelyite is usually white, snow-white, or grayish-white. Less commonly, it is colorless (in the form of well-developed crystals) or takes on yellowish and light brownish hues, which is a result of impurities. No named varieties of this mineral are distinguished. ## History and Name The mineral's name comes from the Hungarian chemist and mine manager, Stephen Szaibély (István Szaibély, 1777-1855), who was the first to study this mineral. Szaibelyite was first described in 1861 by K. F. Peters based on specimens found in the historical Banat region (now in Romania and Serbia). ## Uses Szaibelyite, when occurring in large accumulations, can be a local source of boron. However, its significance is mainly scientific and for collectors.

Properties

Mohs hardness
3-3.5
Luster
Silky, Dull, Earthy
Streak
White
Density
2.6-2.7
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent to opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Szaibelyite is most easily recognized by its characteristic mode of occurrence – as white, light, felted aggregates resembling felt or cotton wool. It is soft and light to the touch. A diagnostic feature is its vigorous reaction with dilute acids. In a blowpipe flame, it melts, coloring the flame green (boron reaction). ## Distinguishing from Similar Minerals Fibrous szaibelyite can be confused with chrysotile asbestos, ulexite, or artinite. It differs from asbestos by its lower hardness and vigorous reaction with acids. Ulexite has a similar appearance but often exhibits the "television stone" effect (fibers transmit images), which is not observed in szaibelyite. Artinite is also a white, fibrous mineral, but it is a magnesium hydroxycarbonate and reacts with acids by releasing carbon dioxide (effervesces). ## Crystal Forms Crystals are very rare, acicular or capillary, and elongated along one axis. They usually form radial or haphazardly tangled fibrous aggregates. Compact, massive, earthy, and chalk-like masses are also commonly found.

Geological environment

## Genesis Szaibelyite is a low-temperature hydrothermal or metamorphic mineral. It forms as a result of the alteration of earlier borates (e.g., ludwigite, kotoite) in magnesium skarns, which are rocks formed at the contact of magmatic intrusions with magnesium-rich carbonate rocks (dolomites, magnesian limestones). It can also crystallize in evaporite salt deposits. ## Mineral Associations This mineral often co-occurs with other magnesium borates, such as ludwigite, kotoite, as well as with fluoborite, brucite, magnetite, serpentine, dolomite, and calcite. ## Localities The most important and classic szaibelyite localities are in Romania (Băița Bihor, formerly Rézbánya) and Serbia. It is also known from Italy (Vesuvius area), Germany (Thuringia), Russia (Urals, Siberia), Kazakhstan (Inder deposit), China, Japan, and the USA (Nevada, California, New Mexico).

Rarity

Not very common

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, even if small, acicular crystals with a silky luster. Pure white, fluffy, and undamaged fibrous aggregates resembling cotton wool or felt, forming aesthetic shapes on the rock matrix, are also highly prized. Contrast with a darker host rock (e.g., with magnetite) enhances the specimen's attractiveness. ## Popular Localities Classic specimens, often of historical significance, come from Băița Bihor in Romania. Large and impressive fibrous aggregates are found in Kazakhstan. In the USA, interesting specimens come from Nevada and California, where szaibelyite occurs in borate deposits.

Care and storage

## Cleaning Szaibelyite specimens, especially those with a delicate, fibrous structure, should be cleaned very carefully. It is best to use compressed air to remove dust. For more compact forms, a soft, dry brush can be used. Contact with water is not recommended. ## What to Avoid This mineral is sensitive to acids, in which it dissolves rapidly. Contact with any chemicals and water, which can damage delicate, fibrous aggregates, should be avoided. It is a brittle and soft mineral, susceptible to mechanical damage. ## Storage It is recommended to store szaibelyite specimens in closed, dry containers or display cases to protect them from dust, moisture, and physical damage. Delicate, "cotton-like" aggregates require special care and are best stored in "micromount" boxes without touching the specimen itself.

Sources

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