Bonaccorsiite

Chemical formula: KK₂Na₃(Al₆Si₃₆)O₈₄

Bonaccorsiite is an extremely rare mineral from the osumilite group, discovered in Italy, forming tiny, hexagonal crystals in volcanic lavas.

## Characteristics Bonaccorsiite is a very rare silicate from the osumilite group, named after mineralogists Elena Bonaccorsi and Stefano Merlino. It occurs as very small, hexagonal, tabular crystals, usually not exceeding 0.1 mm. These crystals are colorless and transparent, with a vitreous luster. Due to its microscopic size, it is a mineral primarily available to specialized collectors and scientific institutions. ## Physical Properties Bonaccorsiite crystals exhibit a hardness of approximately 6 on the Mohs scale. They have a vitreous luster and are transparent. The calculated density is 2.62 g/cm³. The mineral does not show fluorescence under ultraviolet light. ## Colors and Varieties Bonaccorsiite is colorless. No colored varieties or trade names are known. ## History and Name The mineral was discovered in samples from the Case Collina locality, near Pitigliano in Tuscany, Italy. It was approved by the International Mineralogical Association (IMA) in 2007 under number IMA2007-037. The name honors Elena Bonaccorsi and Stefano Merlino, professors of mineralogy at the University of Pisa, for their contributions to silicate research. ## Uses Bonaccorsiite has no industrial application. Its significance is purely scientific and collectible, as an extremely rare member of the osumilite group.

Properties

Mohs hardness: 6
Luster: Vitreous
Streak: White
Density: 2.62
Cleavage: None
Fracture: Uneven
Transparency: Transparent
Crystal system: Hexagonal

Diagnostic features

## Identification Identification of bonaccorsiite is impossible without advanced analytical techniques, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS). In collecting conditions, identification relies solely on a label from a reliable source, confirming previous scientific studies. ## Distinguishing from Similar Minerals It can be confused with other colorless, hexagonal minerals from the osumilite group, such as osumilite itself or yagiite. Differentiation requires specialized analysis of chemical composition, especially the content of potassium, sodium, and magnesium. ## Crystal Forms Bonaccorsiite forms hexagonal, tabular crystals with a hexagonal outline. They occur as single, isolated crystals in small vugs (druses) within volcanic rock.

Geological environment

## Genesis Bonaccorsiite crystallizes in small vugs (druses) within trachyte lavas. It forms in the late stage of volcanic activity, under high-temperature conditions, in an environment rich in silica and alkalis (potassium, sodium). ## Mineral Associations This mineral co-occurs with other rare volcanic minerals such as tridymite, hematite, cristobalite, and other silicates. ## Localities The only confirmed and described locality (type locality) is Case Collina, Pitigliano, Grosseto Province, Tuscany, Italy. This is the only place in the world from which scientific descriptions of this mineral originate.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a bonaccorsiite specimen depends on the abundance of microcrystals in the druse and their visibility. Since the crystals are microscopic, specimens are evaluated under a microscope. The best specimens are those that contain numerous, well-formed crystals on a contrasting host rock background. ## Popular Localities The only source of specimens is the type locality in Pitigliano, Italy. All specimens available on the collector's market come from this single location.

Care and storage

## Cleaning Due to the microscopic size of the crystals and their embedding in the host rock, mechanical cleaning is neither recommended nor possible without specialized equipment. Specimens should be protected from dust. ## What to Avoid Avoid contact with strong acids and chemicals that could damage both the mineral itself and the host rock. Do not subject the specimen to ultrasound or sudden temperature changes. ## Storage Bonaccorsiite specimens should be stored under stable conditions, in closed "micromount" boxes, to protect them from dust and mechanical damage. Direct exposure to sunlight should be avoided, although there is no evidence of fading.

Sources

IMA Mineral List (CNMNC)