Ferro-ferri-pedrizite
Chemical formula: NaLi₂(LiFe²⁺₂Fe³⁺₂)Si₈O₂₂(OH)₂
A black, almost opaque mineral from the amphibole group, discovered in Spain and named after its chemical composition.
Properties
- Mohs hardness
- 6
- Luster
- Vitreous
- Streak
- Grey
- Density
- 0
- Cleavage
- {110}
- Fracture
- Irregular/Uneven
- Transparency
- Opaque
- Crystal system
- Monoclinic
Diagnostic features
## Identification Key diagnostic features include its black color, prismatic crystal form, hardness (6 on the Mohs scale), and gray streak. Its occurrence in a specific geological environment (granitic pegmatites) is also an important clue. Final identification requires advanced chemical analyses (EDS/WDS) and X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other black amphiboles, such as hornblende, arfvedsonite, or riebeckite, as well as schorl tourmaline. Distinguishing it from these minerals based on visual characteristics is very difficult and often impossible without specialized equipment. The streak (gray for ferro-ferri-pedrizite) can be helpful in differentiating it from some of them. ## Crystal Forms It forms elongated, prismatic crystals, often terminated by flat faces. It occurs as single crystals or radial aggregates embedded in the host rock (quartz, albite).
Geological environment
## Genesis This is a magmatic mineral, crystallizing in the late stages of the evolution of granitic pegmatites, rich in lithium and fluorine. ## Mineral Associations It most commonly co-occurs with quartz, albite, microcline, muscovite, and also with other lithium minerals such as elbaite and lepidolite. ## Localities The only confirmed and described occurrence of this mineral in the world is its type locality – Arroyo de la Yedra, Manzanares el Real, in the Community of Madrid, Spain.
Rarity
Extremely rare
For collectors
## Quality Criteria The most valuable specimens are those with well-formed, sharp, and undamaged crystals, clearly contrasting with the light background of the host rock (e.g., white quartz or albite). Crystal size and the overall aesthetic of the composition are crucial. ## Popular Localities The only source of specimens of this mineral is the type locality in Spain. Material from this locality is extremely limited, making it highly sought after by collectors specializing in mineral systematics or rare minerals.
Care and storage
## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush or paintbrush to remove dust. Due to its complex chemical composition, contact with water and cleaning agents should be avoided. ## What to Avoid Avoid contact with all chemicals, acids, and bases, which may react with the mineral's components. The mineral is brittle and sensitive to impact and sudden temperature changes. ## Storage It is recommended to store specimens under stable conditions, in closed display boxes or cabinets, away from dust, humidity, and direct sunlight. They should be protected from mechanical damage.