Nordenskiöldine

Chemical formula: CaSn₄+(BO₃)₂

Nordenskiöldine is a rare calcium tin borate, forming small, tabular crystals with a vitreous luster, prized by collectors of rare minerals.

## Characteristics Nordenskiöldine is a rare mineral from the borate group, chemically classified as a calcium tin borate. It belongs to the dolomite group and is the tin analogue of dolomite and ankerite. It typically occurs as very small, rhombohedral or tabular crystals, often grouped into rosettes or fine-grained aggregates. Crystals rarely exceed a few millimeters in size, and their surfaces can be slightly rounded. ## Physical Properties This mineral is characterized by a hardness of 5.5-6 on the Mohs scale and a relatively high density of approximately 4.2 g/cm³. It has a vitreous luster, and its crystals are usually transparent to translucent. It does not exhibit fluorescence under ultraviolet light. ## Colors and Varieties Nordenskiöldine is most often colorless or pale yellow to yellowish-green. Specimens with sulfur-yellow, honey-yellow, or even brownish hues are sometimes found, which may be related to the presence of impurities. No named varieties are distinguished. ## History and Name The mineral was first described in 1887 by Waldemar Christofer Brøgger. It was named in honor of Adolf Erik Nordenskiöld (1832-1901), a Finnish-Swedish mineralogist, geologist, and explorer who was the first to navigate the Northeast Passage. Type specimens come from the island of Arøya in the Langesundsfjorden region of Norway. ## Uses Due to its rarity and small crystal size, nordenskiöldine has no industrial applications. However, it is a sought-after and valued collector's mineral, especially well-formed crystals from classic localities.

Properties

Mohs hardness: 5.5-6
Luster: Vitreous
Streak: White
Density: 4.17-4.23
Cleavage: Perfect on {1011}
Fracture: Conchoidal to Uneven
Transparency: Transparent to Translucent
Crystal system: Trigonal

Diagnostic features

## Identification Nordenskiöldine is difficult to identify visually without specialized equipment, mainly due to the small size of its crystals. Key features include its trigonal, tabular crystal habit, high density for a non-metallic-looking mineral, and occurrence in specific geological environments (nepheline syenite pegmatites, skarns). ## Distinguishing from Similar Minerals It can be confused with other colorless or yellowish minerals from pegmatites, such as phenakite, herderite, or danburite. It differs from phenakite by its lower hardness. From herderite and danburite, it differs in crystal habit and higher density. However, definitive differentiation requires advanced methods, such as chemical analysis (EDS) to confirm the presence of tin and boron. ## Crystal Forms Crystals are typically small, tabular in habit, often flattened parallel to the rhombohedron base. They occur as single crystals, but more often form fan-shaped or rosette-like aggregates, as well as granular masses.

Geological environment

## Genesis Nordenskiöldine is a mineral of magmatic and metamorphic origin. It most commonly forms in granitic and nepheline syenite pegmatites, where it crystallizes in the late stages of their formation. It is also found in contact skarns, formed at the interface of granitic intrusions with carbonate sedimentary rocks, in zones enriched in boron and tin. ## Mineral Associations This mineral co-occurs with many other pegmatite and skarn minerals. In syenite pegmatites, its typical associated minerals include albite, microcline, aegirine, nepheline, catapleiite, and fluorite. In tin-bearing skarns, it occurs together with cassiterite, vesuvianite, garnets (andradite), danburite, datolite, and axinite-(Fe). ## Localities The most important and classic locality for nordenskiöldine is the Langesundsfjorden area in Norway, from which type specimens originate. Other known localities include the Kola Peninsula in Russia (Lovozero and Khibiny massifs), where it occurs in pegmatites. It is also found in skarns in Pitkäranta in Karelia (Russia), in tin mines in Okayama Prefecture in Japan, and in Franklin, New Jersey, USA.

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with sharp, well-formed, and transparent crystals, ideally forming aesthetic rosettes or groups on a contrasting rock matrix. Crystals with an intense, yellow color are highly valued. Due to their generally small size, specimens with crystals exceeding a few millimeters are considered exceptional. ## Popular Localities Classic specimens, considered exemplary, come from pegmatites in Langesundsfjorden, Norway. Attractive, though usually microscopic, crystals are also found in Russia (Kola Peninsula) and Japan. Specimens from Franklin, USA, are also sought after by specialists.

Care and storage

## Cleaning 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. Ultrasonic cleaners are not recommended, as they can damage delicate crystals. ## What to Avoid Avoid contact with strong acids and other chemicals that may react with borates. The mineral is relatively hard but brittle, so it must be protected from impacts and scratches. It is not sensitive to sunlight. ## Storage Collector's specimens of nordenskiöldine, especially those with well-formed crystals, are best stored in separate, padded boxes or display cases to prevent mechanical damage and contact with harder minerals.

Sources

IMA Mineral List (CNMNC)