Aluminomagnesiohulsite

Chemical formula: Mg<sub>2</sub>AlO<sub>2</sub>(BO<sub>3</sub>)

Aluminomagnesiohulsite is a very rare, black mineral from the hulsite group, being a magnesium and aluminum borate.

## Characteristics Aluminomagnesiohulsite is a mineral from the hulsite group, belonging to the borates. It occurs as elongated, prismatic crystals, which can reach up to 2 mm in length. It usually forms radial aggregates or occurs as single crystals embedded in the rock. Its color is black, and on thin edges, it can be translucent dark brown. ## Physical Properties This mineral is characterized by high hardness, estimated at 6 on the Mohs scale. It has a strong, metallic luster. It is opaque, with the exception of very thin fragments, which can be translucent. The density is approximately 3.73 g/cm³. ## Colors and Varieties Aluminomagnesiohulsite is uniform in color and occurs exclusively in black. No varieties have been distinguished for it. ## History and Name The mineral's name, approved by the IMA in 2002, refers to its chemical composition – the dominance of aluminum (Alumino-) and magnesium (magnesio-) and its structural relationship with hulsite. It was discovered at the Titovskoye deposit in the Tas-Khayakhtakh Mountains in Yakutia (Russia). ## Applications Due to its extreme rarity, aluminomagnesiohulsite has no practical application and is solely an object of scientific and collecting interest for specialized collectors of rare minerals.

Properties

Mohs hardness
6
Luster
Metallic
Streak
Black
Density
3.73
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Opaque,=
Crystal system
Monoclinic

Diagnostic features

## Identification Identifying aluminomagnesiohulsite in the field is practically impossible without specialized equipment. In a collection, it is recognized by its black color, metallic luster, prismatic crystal form, and co-occurrence with other minerals from magnesium skarns. Definitive identification requires chemical analysis (EDS/WDS) and X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other black, prismatic minerals from the hulsite group (hulsite, magnesiohulsite) or tourmaline (schorl). Differentiation from minerals within its own group is only possible through chemical analysis. It differs from tourmaline by its crystallographic system (monoclinic vs. trigonal) and a harder, more metallic luster. ## Crystal Forms It forms elongated, columnar, or acicular crystals with a cross-section close to square. They often occur as radial or chaotic aggregates embedded in calcite or other minerals of the host rock.

Geological environment

## Genesis Aluminomagnesiohulsite forms under conditions of contact metamorphism, in magnesium skarns. It forms at the contact of granitic intrusions with dolomites, in boron-enriched zones. ## Mineral Associations It most often co-occurs with calcite, kotoite, fluoborite, sinhalite, spinel, as well as other minerals from the hulsite group. ## Localities The only confirmed locality of this mineral in the world is its type locality – the Titovskoye boron deposit, in the Tas-Khayakhtakh massif, in Yakutia (Sakha Republic), Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a specimen primarily depends on the size and development of the crystals. Specimens with clearly visible, sharply terminated crystals forming aesthetic, radial aggregates are most valued. Contrast with a light background (e.g., white calcite) also enhances visual and collector value. ## Popular Localities All specimens available on the collector's market come from a single location in the world – the Titovskoye deposit in Russia.

Care and storage

## Cleaning Due to its hardness, it can be cleaned with a soft brush and distilled water. However, caution should be exercised, as specimens are usually small and can be fragile. ## What to Avoid Contact with strong acids, which can damage the mineral, should be avoided. There are no specific recommendations regarding exposure to light or temperature, but as with any rare mineral, stable conditions are recommended. ## Storage Specimens are best stored in closed display boxes to protect them from dust and mechanical damage. Due to the small size of the crystals, caution is advised during handling.

Sources

Read more