Enneasartorite

Chemical formula: Tl₁+₆Pb₂+₃₂As₃+₇₀S₂-₁₄₀

Enneasartoryte is an extremely rare, lead-gray thallium and lead sulfarsenide, occurring as tiny, embedded grains in dolomitic rocks in the Lengenbach quarry in Switzerland.

## Characteristics Enneasartoryte is a very rare mineral from the sulfosalt group, with a complex chemical composition containing thallium, lead, arsenic, and sulfur. Its name refers to its close relationship with sartoryte and its nine times larger unit cell. It typically forms very small, anhedral (not exhibiting external crystal forms) grains, which are embedded in the rock matrix, most often in dolomite. It is observed as aggregates up to 1-2 mm in size. Due to its appearance and mode of occurrence, it is a mineral impossible to identify with the naked eye. ## Physical Properties This mineral is characterized by a metallic luster and is opaque. Its hardness on the Mohs scale ranges from 3 to 3.5, classifying it as a soft mineral. The density of enneasartoryte is high, approximately 5.55 g/cm³. ## Colors and Varieties Enneasartoryte has a steel-gray to lead-gray color, and a metallic luster is visible on fresh fracture surfaces. No color varieties or commercial varieties are known. ## History and Name Enneasartoryte was first described in 2015 by a team of mineralogists (S. Graeser, D. Topa, E. Makovicky, W.H. Paar). Its name comes from the Greek word *ennéa* (ἐννέα), meaning "nine," and the name of the mineral sartoryte. This name reflects the fact that the *c* parameter of enneasartoryte's unit cell is nine times larger than that of sartoryte, indicating their structural kinship. It was approved by the International Mineralogical Association (IMA) under number 2014-093. The type locality (locus typicus) is the Lengenbach quarry in the Binn Valley, Valais Canton, Switzerland. ## Uses Enneasartoryte has no practical applications. Its significance is purely scientific and collectible, as a unique and very rare representative of complex sulfosalts.

Properties

Mohs hardness: 3-3.5
Luster: Metallic
Streak: Black
Density: 5.55
Cleavage: Perfect on {100}
Fracture: Uneven
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of enneasartoryte under amateur conditions is practically impossible. This mineral occurs as microscopic, embedded grains with a metallic luster, indistinguishable to the naked eye from many other co-occurring sulfosalts. Definitive identification requires advanced analytical techniques, such as electron probe microanalysis (EPMA) to determine chemical composition and X-ray diffraction (XRD) for crystal structure analysis. ## Distinguishing from Similar Minerals Enneasartoryte is visually indistinguishable from other rare sulfosalts of the sartoryte group found in the Lengenbach quarry, such as sartoryte, baumhauerite, dufrénoysite, or rathite. All these minerals form similar, gray-metallic aggregates embedded in dolomite. Differentiation is possible only through detailed laboratory studies. ## Crystal Forms Enneasartoryte forms anhedral grains, meaning they lack their own crystal faces, up to about 0.5 mm in size, which coalesce into irregular aggregates reaching up to 2 mm. These crystals are always embedded in dolomitic rock.

Geological environment

## Genesis Enneasartoryte forms as a result of low-temperature hydrothermal processes that affected sulfide deposits in dolomitic rocks. This mineralization is associated with Alpine metamorphic fluids that were rich in arsenic, lead, thallium, and sulfur. It crystallized in fissures and small cavities within saccharoidal dolomite. ## Mineral Associations This mineral occurs in close association with other, often equally rare, lead and arsenic sulfosalts. It is most commonly accompanied by realgar, sartoryte, baumhauerite, rathite, dufrénoysite, and rock-forming minerals such as dolomite and quartz. ## Localities The only known worldwide occurrence of enneasartoryte is its type locality – the Lengenbach quarry in the Binn Valley (Binnental), Valais Canton, Switzerland. This site is famous for its exceptional richness and diversity of rare thallium, lead, and arsenic sulfosalts.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of an enneasartoryte specimen is primarily assessed based on its scientific confirmation and the richness of its association. Since the mineral forms only microscopic inclusions, its aesthetic value is limited. The most desirable specimens are those in which enneasartoryte aggregates are relatively large (on a micro scale) and clearly visible against the contrasting dolomite. A label with analytically confirmed mineral identification is crucial. The presence of well-formed crystals of associated minerals, such as realgar, can enhance the specimen's attractiveness. ## Popular Localities The only source of enneasartoryte specimens is the Lengenbach quarry in Switzerland. Specimens from this location are highly valued by specialized collectors of rare minerals and micromounts.

Care and storage

## Cleaning Enneasartoryte specimens, due to their occurrence as small, embedded grains in the rock matrix, generally do not require and should not be subjected to intensive cleaning. If necessary, dust can be removed with a soft brush or a gentle stream of compressed air. ## What to Avoid Avoid contact with water, acids, and other chemicals that could react with the mineral or the surrounding rock (dolomite). The mineral is soft and brittle, so it should be protected from impacts, scratching, and vibrations. As a mineral containing thallium and arsenic, avoid inhaling dust and wash hands after any contact with the specimen. ## Storage Specimens should be stored under stable conditions, in a dry place, away from direct sunlight and heat sources. The best solution is to store them in a closed display box, which protects the specimen from dust and mechanical damage.

External references

https://en.wikipedia.org/wiki/https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FEnneasartorite