Emmerichite
Chemical formula: Ba₂Ti⁴⁺₂Na₃Fe³⁺(Si₂O₇)₂O₂F₂
Emmerichite is a very rare mineral from the aenigmatite group, characterized by a complex chemical composition and occurrence in volcanic eifelites.
Properties
- Mohs hardness
- 3-4
- Color
- brown
- Luster
- Metallic
- Streak
- white
- Density
- 3.864
- Cleavage
- on {100}
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Amateur identification of emmerichite is practically impossible due to the microscopic size of its crystals and its resemblance to other black minerals. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS). ## Distinguishing from similar minerals Emmerichite can be confused with other rare minerals from the aenigmatite group, such as aenigmatite, krinovite, or rhönite, as well as with more common minerals like ilmenite or magnetite, which often co-occur in the same environment. Differentiation relies solely on chemical and crystallographic analysis. ## Crystal forms It forms small, tabular or lath-like crystals, often arranged in radial aggregates. Crystals are elongated along the [100] axis and flattened parallel to {010}.
Geological environment
## Genesis Emmerichite forms under volcanic conditions, in the late stages of magma crystallization. It occurs in cavities and small druses within eifelites – a specific, leucite- and nepheline-rich effusive rock associated with alkaline volcanism. ## Mineral associations This mineral co-occurs with a number of other minerals typical of this environment, such as augite, apatite, enstatite, hematite, ilmenite, leucite, magnetite, nepheline, phlogopite, and pseudobrookite. ## Localities The only confirmed locality of emmerichite in the world (type locality) is the "In den Dellen" quarry in the Mendig region, in the Eifel mountains, in the state of Rhineland-Palatinate, Germany.
Rarity
Extremely rare
For collectors
## Quality criteria The quality of emmerichite collector specimens primarily depends on the size and development of the crystals, although even the largest ones are microscopic. Most valued are specimens with clearly visible, sharp crystals or their radial aggregates, embedded in a contrasting host rock. Association with other rare minerals is also important. ## Popular localities The only source of emmerichite specimens is its type locality – the "In den Dellen" quarry in Germany. All specimens available on the collector's market originate from this single location.
Care and storage
## Cleaning Emmerichite specimens should be cleaned very carefully, preferably using compressed air to remove dust. Avoid washing in water, and especially avoid using ultrasonics, which can damage delicate crystals. ## What to avoid Avoid contact with chemicals, acids, and detergents. The mineral is stable, but it should be protected from extreme temperatures and mechanical shocks. ## Storage It is recommended to store specimens in specialized micromount boxes, which protect them from dust, moisture, and mechanical damage. Exposure to strong light is not advisable, although there is no evidence of its degrading effect.