Magnesio-lucchesiite

Chemical formula: CaMg₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₃O

Magnesio-lucchesiite is a very rare mineral from the tourmaline group, distinguished by its unique chemical composition and dark color.

## Characteristics Magnesio-lucchesiite is a mineral belonging to the tourmaline group. It forms elongated, prismatic crystals, often terminated pyramidally, which can reach up to 2 cm in length. They usually occur as radial aggregates. It is an opaque mineral, black in color with a vitreous luster. ## Physical Properties This mineral is characterized by a Mohs hardness of 7. Its density is estimated at approximately 3.18 g/cm³. It has a vitreous luster and a black streak. It exhibits no cleavage, and its fracture is uneven to conchoidal. ## Colors and Varieties Magnesio-lucchesiite is an idiochromatic mineral, meaning its color is constant and directly results from its chemical composition. It occurs exclusively in black. No color or commercial varieties are distinguished. ## History and Name The name "magnesio-lucchesiite" refers to its chemical composition – the dominance of magnesium (magnesio) – and is a tribute to Fabrizio Lucchesi (born 1953), an Italian mineralogist and crystallographer from Sapienza University of Rome, for his contributions to research on the tourmaline group. The mineral was officially approved by the International Mineralogical Association (IMA) in 2019 (IMA2019-022). ## Uses Due to its extreme rarity, magnesio-lucchesiite has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for specialized collectors of rare and systematic minerals.

Properties

Mohs hardness: 7
Luster: Vitreous
Streak: Black
Density: 3.18
Cleavage: None
Fracture: Uneven to conchoidal
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Identification of magnesio-lucchesiite is based on its characteristic appearance – black, prismatic crystals, often in radial aggregates. Key features include black color, vitreous luster, and high hardness (7 on the Mohs scale). Final identification is only possible using advanced analytical methods, such as spectroscopy and chemical analysis, due to its similarity to other black tourmalines. ## Distinguishing from Similar Minerals Magnesio-lucchesiite is visually indistinguishable from other black tourmalines, such as schorl or dravite. The differences lie in the chemical composition, particularly in the content of magnesium, calcium, and aluminum, and in the details of the crystal structure. Without specialized laboratory tests, it cannot be distinguished from them. ## Crystal Forms This mineral forms well-developed, elongated crystals with a prismatic habit, featuring characteristic vertical striations on the faces. Crystals are often terminated by pyramidal faces. It also occurs as radial or fibrous aggregates.

Geological environment

## Genesis Magnesio-lucchesiite forms under specific metamorphic conditions. Its occurrence is associated with rocks rich in magnesium and boron that have undergone contact metamorphism in contact zones with magmatic intrusions. In its type locality (Mogok, Myanmar), it was found in forsterite-spinel skarns. ## Mineral Associations This mineral co-occurs with other minerals typical of metamorphic and skarn environments. Its paragenesis includes minerals such as forsterite, spinel, sinhalite, pargasite, fluorite, chondrodite, phlogopite, calcite, dolomite, graphite, and other minerals from the tourmaline group. ## Localities The only confirmed and described occurrence of magnesio-lucchesiite in the world is its type locality: the Pein-Pyit mines in the Mogok District, Mandalay Region, Myanmar (Burma).

Rarity

Extremely rare

For collectors

## Quality Criteria The most highly prized magnesio-lucchesiite specimens are those with well-formed, sharply terminated crystals with a strong luster. Specimens where crystals are isolated or form aesthetic, radial aggregates on a contrasting rock matrix are particularly desirable. Due to the scientific nature of the mineral, analytically confirmed identity of the specimen is crucial. ## Popular Localities As this mineral is known from only one location in the world, all specimens available on the collector's market originate from the mines in the Mogok area of Myanmar. This is the sole source of material for collectors and scientific institutions.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush to remove dust. Due to the risk of reaction with water and chemicals, wet cleaning should be avoided. ## What to Avoid Contact with water, acids, and other chemical agents must be strictly avoided. The mineral is sensitive to moisture. It should not be heated or subjected to ultrasound. Prolonged exposure to sunlight is not recommended. ## Storage It is recommended to store specimens in a dry place, preferably in a sealed, closable display box away from sources of moisture. It is advisable to use desiccants (e.g., silica gel) to ensure stable conditions.

Sources

IMA Mineral List (CNMNC)