Pyroxferroite
Chemical formula: Fe<sup>2+</sup>SiO<sub>3</sub>
Pyroxferroite is a rare iron silicate from the pyroxenoid group, originally discovered in lunar rock samples brought back by the Apollo 11 mission.
Properties
- Mohs hardness
- 5.5
- Luster
- Vitreous
- Streak
- Pale brown
- Density
- 3.86
- Cleavage
- Perfect on {110} and {100}
- Fracture
- Uneven
- Transparency
- Translucent to Opaque
- Crystal system
- Triclinic
Diagnostic features
## Identification Amateur identification of pyroxferroite is practically impossible and requires advanced analytical methods, such as X-ray diffraction (XRD) or X-ray microanalysis (EDS/WDS). Its pale yellow color, occurrence in specific associations, and crystal habit can be indicative but are not definitive characteristics. ## Distinguishing from Similar Minerals It can be confused with other iron and magnesium silicates, such as pyroxenes (e.g., ferrosilite, hedenbergite) or olivines (fayalite). Differentiation requires specialized laboratory equipment, as physical properties (color, hardness) are very similar. Pyroxferroite is unstable at low pressure and temperature, which distinguishes it from ferrosilite. ## Crystal Forms It forms elongated, tabular, or bladed crystals with a nearly rectangular cross-section. It often occurs as small grains embedded in rock or as radial aggregates.
Geological environment
## Genesis Pyroxferroite is a high-pressure mineral. On Earth, its formation is associated with contact or regional metamorphism processes under high pressure and relatively low temperature, in iron-rich rocks such as iron formations. It also forms under shock conditions (shock metamorphism) in impact craters. Its most famous occurrences are in lunar basalts, where it crystallized from magma under conditions of low oxygen fugacity and high pressure. ## Mineral Associations In lunar rocks, it co-occurs with clinopyroxenes, plagioclase, ilmenite, tridymite, and fayalite. In terrestrial iron formations, it is accompanied by quartz, magnetite, hedenbergite, fayalite, eulite, and almandine. ## Localities The most famous origin is the Sea of Tranquility on the Moon (Apollo 11 mission). On Earth, its presence has been confirmed in a few localities, including mines in Labrador City, Canada; in Ivaara, Finland; in the Isua formation in Greenland; and in the Manicouagan impact crater in Quebec, Canada.
Rarity
Very rare
For collectors
## Quality Criteria The collector appeal of pyroxferroite is determined primarily by its origin and scientific context, rather than aesthetic qualities. Microscopic samples documented as originating from lunar rocks are the most desirable. For terrestrial specimens, the richness of crystals in the host rock and a precisely determined locality increase value. Well-formed, even if small, crystals are more valuable than amorphous grains. ## Popular Localities By far the most valued and known "locality" is the Sea of Tranquility on the Moon. Among collectors specializing in rare minerals or micromounts, specimens from classic terrestrial localities, such as Labrador City in Canada, are sought after.
Care and storage
## Cleaning Pyroxferroite specimens should only be cleaned with compressed air or a very soft brush. Contact with water and chemicals should be avoided, as the mineral is unstable under surface conditions and may undergo alteration. ## What to Avoid Ultrasonic cleaners, steam cleaners, acids, solvents, and all detergents must be absolutely avoided. The mineral is sensitive to moisture and temperature changes. It should not be heated or exposed to prolonged sunlight. ## Storage It is recommended to store specimens in dry, stable conditions, preferably in sealed containers or display cases with humidity control (e.g., using silica gel). It should be protected from dust and mechanical damage.