Niningerite
Chemical formula: MgS<sup>2-</sup>
Niningerite is a rare magnesium sulfide, found almost exclusively in meteorites known as enstatite chondrites.
Properties
- Mohs hardness
- 3.5-4
- Luster
- Metallic
- Streak
- Black
- Density
- 2.91
- Cleavage
- Perfect on {100}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Cubic
Diagnostic features
## Identification Identifying niningerite is extremely difficult without specialized equipment. It requires chemical analysis (e.g., using an electron microprobe) and X-ray diffraction (XRD) to confirm its composition (magnesium sulfide) and crystal structure. Visually, it is simply a small, black or gray, metallic grain within the meteorite rock. ## Distinguishing from Similar Minerals It can be confused with other fine-grained, opaque minerals found in meteorites, such as troilite (FeS), graphite (C), or chromite. Differentiation relies solely on laboratory analysis of chemical composition – niningerite is distinguished by its high magnesium content. ## Crystal Forms It forms very small, isometric crystals with a cubic or octahedral habit. Most often, it occurs as irregular grains intergrown with other minerals.
Geological environment
## Genesis Niningerite is a mineral characteristic of a very specific environment – enstatite chondrites. These are meteorites that formed under highly reducing (anaerobic) conditions and at high temperatures, likely in the inner part of the solar nebula. Under such conditions, magnesium, instead of forming silicates, combined with sulfur. ## Mineral Associations This mineral co-occurs with other minerals typical of enstatite chondrites, such as enstatite, clinoenstatite, kamacite, perryite, oldhamite, troilite, and various phosphides and silicides of metals. ## Localities Its occurrence is limited to enstatite chondrites. It has been identified, among others, in the Abee meteorite (Alberta, Canada – type locality), Adhi Kot (Pakistan), Indarch (Azerbaijan), Qingzhen (China), and Saint-Sauveur (France).
Rarity
Very rare
For collectors
## Quality Criteria From a collector's perspective, the value of a specimen containing niningerite primarily depends on the value of the meteorite itself in which it is found. Since niningerite grains are microscopic, their individual quality is not assessed. What matters is the well-documented provenance of the meteorite and the presence of the mineral confirmed by analyses. The most valuable specimens are those from type localities or from rare, well-studied falls. ## Popular Localities The most known and historically important source is the Abee meteorite from Canada. Other meteorites in which niningerite has been identified, such as Indarch or Qingzhen, are also valued by collectors specializing in meteorites.
Care and storage
## Cleaning Specimens containing niningerite, due to their sensitivity to moisture and oxygen, should generally not be wet-cleaned. Dust can be removed very carefully with a soft brush or compressed air from a safe distance. ## What to Avoid Contact with water, water vapor, and high humidity must be strictly avoided, as niningerite readily reacts with water, undergoing decomposition. It must also be protected from oxygen, which causes its oxidation. No chemical agents should be used. ## Storage Storage requires specialized conditions. Specimens are best kept in airtight containers with a desiccant (silica gel) or in an inert gas atmosphere (e.g., argon). Display should be in closed, sealed showcases with controlled humidity.