Stangersite

Chemical formula: Sn₂+Ge₄+S₂-₃

Stangerite is an extremely rare tin and germanium sulfide, forming tiny, black, metallic crystals, discovered in a volcanic complex on Kamchatka.

## Characteristics Stangerite is a sulfide mineral with a complex chemical composition, containing tin and germanium. It occurs as very fine, tabular or lath-like crystals, reaching sizes up to 10x30x150 micrometers. It also forms irregular grains. It is black and opaque, with a metallic luster. It usually occurs as inclusions in other minerals, mainly in ottemannite. ## Physical Properties Due to the extremely small size of the crystals, most physical properties, such as hardness, density, or fracture, have not been precisely determined. The luster is metallic, and the streak is black. ## History and Name The mineral was approved by IMA in 2013 (IMA2013-069). Its name honors Allan Stanger, an Australian chemist and mineral collector, in recognition of his contributions to analytical mineral chemistry. It was discovered in samples from the fumaroles of Kudryavy volcano on Iturup Island (Kuril Archipelago), in an area administratively belonging to Russia.

Properties

Luster: Metallic
Streak: Black
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of stangerite is impossible without advanced laboratory techniques. Due to its microscopic size and occurrence as inclusions, it requires analysis using a scanning electron microscope (SEM) with an EDS detector (energy-dispersive spectrometry) to confirm its chemical composition (presence of tin, germanium, and sulfur). Optically, it is simply a black, metallic grain. ## Distinguishing from similar minerals It can be confused with other rare sulfides found in the same environment, such as herzenbergite, ottemannite, or teallite. Differentiation is based solely on precise chemical analysis. ## Crystal forms It forms very small, elongated, lath-like or tabular crystals. It also occurs as irregular grains and aggregates, often as inclusions in other minerals.

Geological environment

## Genesis Stangerite forms in a unique environment of high-temperature (450–650°C) volcanic exhalations (fumaroles). It crystallizes directly from volcanic gases rich in sulfur, tin, and germanium under strongly reducing conditions. It is a mineral typical of volcanic sublimation processes. ## Mineral associations This mineral has been found in paragenesis with other rare sulfides and sulfosalts. It most commonly co-occurs with ottemannite (in which it forms inclusions), as well as with herzenbergite, teallite, greenockite, and cannizzarite. ## Localities The only confirmed locality of stangerite in the world (type locality) are the active fumaroles of Kudryavy volcano, located on Iturup Island in the Kuril Islands archipelago (Sakhalin Oblast, Russia).

Rarity

Extremely rare

For collectors

## Quality criteria From a collector's perspective, stangerite is an object of almost exclusively scientific and systematic importance. It does not form macroscopic specimens. The only value is the mere fact of possessing a documented sample from the type locality, containing this mineral, confirmed by analysis. Such a specimen will be a fragment of rock or an aggregate of other minerals with microscopic stangerite inclusions. ## Popular localities The only source of material is the type locality – Kudryavy volcano in the Kuril Islands. Obtaining specimens is extremely difficult and limited to scientific expeditions.

Care and storage

## Cleaning Due to its extreme rarity and microscopic crystal size, stangerite specimens are not subject to cleaning in the traditional sense. Any attempt at mechanical or chemical cleaning would destroy the delicate crystals. Specimens should be treated solely as research and archival objects. ## What to avoid Absolutely everything should be avoided: contact with chemicals, ultrasound, temperature changes, humidity, and any mechanical manipulation. The mineral is sensitive to oxidation. ## Storage Specimens containing stangerite should be stored under stable conditions, in specialized, sealed containers (so-called micromount boxes), away from light, dust, and humidity fluctuations. The safest place is a scientific institution's archive.

Sources

IMA Mineral List (CNMNC)