Hansesmarkite
Chemical formula: Ca<sub>2</sub>Mn<sup>2+</sup><sub>2</sub>Nb<sup>5+</sup><sub>6</sub>O<sub>19</sub>·20H<sub>2</sub>O
Hansesmarkite is an extremely rare, hydrated calcium manganese niobate, forming orange-yellow, platy crystals.
Description
## Characteristics Hansesmarkite is a mineral from the niobate group, characterized by a complex chemical composition and a high degree of hydration. It occurs as small aggregates, composed of thin, bladed or platy crystals, which often arrange themselves into divergent or nearly parallel packets. Its small size makes it a typical micromount mineral. ## Physical Properties Hansesmarkite crystals are brittle and delicate. This mineral has a vitreous luster and is translucent. Its Mohs hardness has not been determined, but due to its structure and composition, it can be assumed to be a soft mineral. The density calculated based on the formula and unit cell parameters is 2.99 g/cm³, while the measured density is unknown. ## Colors and Varieties Hansesmarkite has a characteristic, vivid color, ranging from orange-yellow to yellowish-brown. No color varieties or commercial varieties are known. ## History and Name The mineral was described in 2007 by a group of mineralogists (G. Raade, G. Ferraris, A. G. Criddle, K. T. Fehr). Its name honors Hans Eskil Hansesmark (1923–2009), a Norwegian collector and amateur mineralogist who found the first specimens of this mineral on the island of Låven in Langesundsfjorden, Norway. This is the only known locality of this mineral in the world (localitas typica). ## Applications Due to its extreme rarity and occurrence as microscopic specimens, hansesmarkite has no industrial applications. It is solely an object of scientific interest and a prized acquisition for specialized collectors of rare minerals and micromounts.
Diagnostic features
## Identification Characteristic features of hansesmarkite include its intense orange-yellow color, the form of thin, platy crystals forming aggregates, and its genesis and paragenesis. A key diagnostic clue is its extreme rarity and origin from the only known locality in the world - Langesundsfjorden in Norway. ## Distinguishing from Similar Minerals In its type locality, hansesmarkite may be confused with other rare, yellow or orange secondary minerals. Its unique crystal habit (thin plates/blades) and specific association with other minerals of nepheline syenite pegmatites aid in identification. However, definitive identification requires advanced analytical techniques, such as X-ray diffraction (XRD) or chemical microanalysis (EDS), which is standard for micromount minerals. ## Crystal Forms Hansesmarkite forms aggregates of thin, elongated crystals with a bladed or platy cross-section. Individual crystals rarely exceed fractions of a millimeter in length and are gathered in fan-shaped or radial clusters.
Geological environment
## Genesis It is a secondary mineral, formed in the late stage of hydrothermal processes. It crystallizes at low temperatures in voids and fissures (miaroles) within nepheline syenite pegmatites. ## Mineral Associations Hansesmarkite occurs in association with other minerals typical of the Langesundsfjorden pegmatites, such as aegirine, albite, analcime, catapleiite, eudidymite, lorenzenite, natrolite, and serandite. ## Localities The only confirmed and described locality of hansesmarkite in the world is Låven island in the Langesundsfjorden geological complex, in the Larvik area (Vestfold, Norway).
Rarity
Extremely rare
Collector aspects
## Quality Criteria The quality of collectible hansesmarkite specimens, which occur exclusively as micromounts, is assessed based on several criteria. The most important is the abundance and size of crystal aggregates on the rock matrix. Specimens with well-formed, undamaged clusters of intense, orange-yellow color are more highly valued. An additional advantage is the aesthetic combination with well-developed crystals of other rare associated minerals. ## Popular Localities Hansesmarkite specimens come exclusively from one locality in the world - the historical locality on Låven island in Norway. Material from this locality is extremely difficult to obtain.
Care and storage
## Cleaning Hansesmarkite specimens are extremely delicate and sensitive. Cleaning should be kept to an absolute minimum. Only very careful dust removal with a soft, dry brush or a stream of compressed air used from a distance and at minimal pressure is permissible. Contact with water, chemicals, and ultrasonic cleaners must be strictly avoided. ## What to Avoid Hansesmarkite is a highly hydrated mineral (containing 20 water molecules in its structure), which makes it extremely sensitive to changes in humidity and temperature. Heating or storage in dry air leads to irreversible dehydration, as a result of which the mineral dulls, disintegrates, and is destroyed. It should be protected from direct sunlight, heat sources, and sudden fluctuations in environmental conditions. ## Storage It is recommended to store specimens in tightly sealed containers, such as micromount boxes, which help maintain a stable humidity level. Store in a dark and cool place, away from heaters and lamps.