Carlosturanite

Chemical formula: (Mg,Fe₂+,Ti₄+)₂₁(Si,Al)₁₂O₂₈(OH)₃₄·H₂O

Carlosturanite is a rare, fibrous mineral from the serpentine group, forming asbestos-like aggregates with a silky luster.

## Characteristics Carlosturanite is a mineral belonging to the broad serpentine group, characterized by a strongly fibrous structure. It occurs as flexible, easily separable fibers that can form felted or matted aggregates, resembling asbestos in appearance. Individual fibers are flexible and have a silky luster, which gives the aggregates a characteristic appearance. This mineral is opaque and soft. ## Physical Properties The hardness of carlosturanite on the Mohs scale is very low, approximately 1, which means it is an exceptionally soft mineral. Its fibers are flexible. It has a density of approximately 2.56 g/cm³. The luster is typically silky, especially noticeable on fibrous aggregates. ## Colors and Varieties Carlosturanite most commonly ranges in color from brown to reddish-brown. No distinct color varieties or commercial varieties have been identified. ## History and Name The mineral was named in honor of Professor Carlo Sturani (1938-1976), an Italian geologist from the University of Turin, who made significant contributions to the study of the geology of the Western Alps. Carlosturanite was approved as a new mineral by the International Mineralogical Association (IMA) in 1984. ## Uses Due to its rarity and fibrous nature, carlosturanite is solely of interest to collectors and a subject of scientific research. It has no industrial applications.

Properties

Mohs hardness: 1
Luster: Silky
Streak: Pale brown
Density: 2.56
Cleavage: Perfect on {001}
Fracture: Splintery
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Carlosturanite can be identified by its characteristic, strongly fibrous, asbestos-like form. Key features include its brown color, silky luster, low hardness (approximately 1 on the Mohs scale), and the flexibility and pliability of its fibers. ## Distinguishing from Similar Minerals This mineral can be confused with other fibrous serpentines, such as chrysotile (serpentine asbestos). Chrysotile is typically greenish, yellowish, or white, whereas carlosturanite is typically brown. Definitive differentiation requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms Carlosturanite forms elongated, lath-like, or fibrous crystals that combine into flexible, often felted or matted aggregates. Single, well-formed crystals are extremely rare.

Geological environment

## Genesis Carlosturanite forms as a result of hydrothermal and metamorphic processes within ultramafic rocks, such as serpentinites. It forms in veins cutting through serpentinite, often in association with other minerals from this group. ## Mineral Associations This mineral co-occurs with other serpentine minerals, such as chrysotile, antigorite, and lizardite. It is also often accompanied by brucite, diopside, magnetite, and garnets from the grossular-andradite group. ## Localities The most important and classic localities from which the best-known carlosturanite specimens originate are in Italy, in the Piedmont region. These include Sampeyre in the Val Varaita valley and the Val Lanzo valley. This mineral has also been identified in serpentinites in Japan (Tari-Komi mine in Hyōgo Prefecture) and in Switzerland (Zermatt area).

Rarity

Very rare

For collectors

## Quality Criteria The most prized carlosturanite specimens are those that exhibit well-defined, long, and flexible fibers with an intense silky luster. The appeal is also enhanced by a contrasting serpentinite matrix and the presence of associated minerals, such as green diopside or black magnetite. Specimens with a rich, brown color are more sought after than lighter ones. ## Popular Localities By far the most desired specimens by collectors come from the classic Italian localities in the Piedmontese Alps, especially from Sampeyre and Val Lanzo. These are considered typical material for this mineral and represent a quality standard.

Care and storage

## Cleaning Carlosturanite specimens are very delicate and should be handled with care. For cleaning, it is best to use compressed air to remove dust. Avoid contact with water, which can weaken the cohesion of fibrous aggregates. ## What to Avoid Absolutely avoid contact with chemicals, acids, and detergents. The mineral is very soft, so protect it from scratches and impacts. The fibrous structure is prone to disintegration, so avoid crushing and friction. ## Storage It is recommended to store specimens in closed, padded boxes or display cases to protect them from mechanical damage and dust. Avoid exposure to vibrations and shocks.

Sources

IMA Mineral List (CNMNC)