Ferroinnelite
Chemical formula: Ba₄Ti⁴⁺₂Na(NaFe²⁺)Ti⁴⁺(Si₂O₇)₂[(S⁶⁺O₄)(PO₄)]O₂[O(OH)]
Ferroinnelite is a very rare, brown mineral from the innelite group, discovered in the Khibiny Massif in Russia, distinguished by its complex chemical composition.
Properties
- Mohs hardness
- 5-0
- Color
- yellow to yellow brown
- Luster
- Vitreous, Pearly
- Streak
- white
- Density
- 4.088
- Cleavage
- {001} medium
- Fracture
- Irregular/Uneven
- Transparency
- Transparent
- Crystal system
- Triclinic
Diagnostic features
## Identification Ferroinnelite can be identified by its characteristic platy or tabular habit, brown color, and pearly luster on cleavage surfaces. Its occurrence is restricted to a specific geological environment – agpaitic pegmatites. ## Distinguishing from Similar Minerals It can be confused with other minerals from the innelite group, such as innelite itself. Differentiation requires advanced analytical methods, such as chemical analysis (EDS/WDS) to confirm the dominance of iron. Visually, it may resemble some micas (e.g., biotite), but it differs from them in hardness, density, and occurrence environment. ## Crystal Forms Crystals are tabular, elongated, and flattened. They typically form aggregates with a radial or fan-like structure, as well as irregular platy clusters.
Geological environment
## Genesis Ferroinnelite forms in highly differentiated, alkaline agpaitic pegmatites. It is a late-stage crystallization mineral in these specific intrusions. ## Mineral Associations This mineral co-occurs with other rare alkaline minerals. In its type locality (Khibiny Massif), it was found in association with aegirine, nepheline, microcline, sodalite, eudialyte, lorenzenite, lamprophyllite, and other minerals from the innelite group. ## Localities The only confirmed and described locality for ferroinnelite in the world is its type locality: the Khibiny Massif on the Kola Peninsula in the Murmansk Oblast, Russia.
Rarity
Extremely rare
For collectors
## Quality Criteria The most valuable ferroinnelite specimens are those with well-formed, sharply terminated crystals of distinct tabular form, grouped into aesthetic, radial aggregates. An intense, reddish-brown color and good luster are desirable. Size is important, but even microscopic, yet well-formed crystals are valuable from a scientific perspective. ## Popular Localities The only source of specimens of this mineral is the Khibiny Massif in Russia. Specimens from this location are highly sought after by collectors specializing in rare mineral species and minerals from alkaline pegmatites.
Care and storage
## Cleaning Ferroinnelite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its brittleness and platy nature, washing in water, and especially using ultrasonic cleaners, should be avoided. ## What to Avoid Avoid contact with acids and other chemicals that can damage the mineral's surface. It is brittle, so protect it from impacts and scratches. Do not heat it or expose it to sudden temperature changes. ## Storage It is recommended to store specimens in separate, padded collector's boxes to prevent mechanical damage. Protect it from dust and moisture.