Hendekasartorite
Chemical formula: Tl¹⁺₂Pb²⁺₄₈As³⁺₈₂S²⁻₁₇₂
Hendekasartorite is a rare, lead-gray sulfosalt of lead, arsenic, and thallium, occurring as small, embedded grains.
Properties
- Mohs hardness
- 3-3.5
- Color
- Lead-grey, grey
- Streak
- Dark brown
- Density
- 5.18
- Cleavage
- {100}
- Fracture
- Conchoidal
- Transparency
- Opaque
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identifying hendekasartorite is extremely difficult and practically impossible without advanced analytical methods, such as X-ray microanalysis (EDS/WDS) and X-ray diffraction (XRD). In collecting contexts, identification relies almost exclusively on a label from a reputable source confirming analysis. Visual characteristics, such as lead-gray color, metallic luster, and occurrence in Lengenbach marble, are merely indicative. ## Distinguishing from Similar Minerals The mineral is visually indistinguishable from other rare sulfosalts of the sartorite group found in the same locality, such as sartorite, dufrénoysite, baumhauerite, or rathite. All form similar, gray, metallic inclusions in dolomite. Definitive distinction requires specialized laboratory equipment. ## Crystal Forms It typically forms anhedral, irregular grains up to several hundred micrometers in size. Subhedral (partially developed), elongated crystals are very rarely observed.
Geological environment
## Genesis Hendekasartorite forms as a result of hydrothermal processes in metamorphic deposits. It occurs in veins cutting Triassic dolomitic marbles (saccharoidal limestones). Its crystallization is associated with the presence of solutions rich in lead, arsenic, thallium, and sulfur. ## Mineral Associations This mineral coexists with other rare lead and arsenic sulfosalts, which is typical for its type locality. It is most commonly associated with sartorite, dufrénoysite, baumhauerite, rathite, realgar, orpiment, as well as dolomite and pyrite. ## Localities The only confirmed and described occurrence of hendekasartorite in the world is the Lengenbach quarry, in the Binn Valley, Valais canton, Switzerland. This is a classic locality for many rare thallium sulfosalts.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a hendekasartorite specimen is primarily assessed based on confirmation of its identity through chemical analysis. Since the mineral forms microscopic grains, collector specimens are typically fragments of the host rock (dolomite) with visible, embedded, metallic aggregates. Specimens with a richer concentration of the mineral or with rare, partially formed crystals would be exceptionally valued. Accurate documentation and a label from a reputable source are crucial. ## Popular Localities The only source of collector specimens is the type locality – the Lengenbach quarry in Switzerland. Material from this location is highly sought after by collectors specializing in mineral systematics and rare species.
Care and storage
## Cleaning Hendekasartorite specimens, usually in the form of tiny grains within the host rock, are very delicate. Cleaning should be kept to an absolute minimum. If necessary, compressed air can be used to remove dust. Contact with water and any chemical agents should be avoided. ## What to Avoid Avoid ultrasonic cleaners, acids, detergents, and solvents. The mineral is soft and susceptible to scratching. As a sulfosalt, it may be prone to oxidation in humid environments, so it should be protected from moisture and sudden temperature changes. ## Storage It is recommended to store specimens under stable conditions, in sealed, dry containers (e.g., "micromount" boxes) away from light and contaminants. Due to the presence of toxic elements (lead, arsenic, thallium), it should be stored out of reach of children and pets, and hands should be washed after handling the mineral.