Fuenzalidaite
Chemical formula: K₃Na₅Mg₅(I⁵⁺O₃)₆(S⁶⁺O₄)₆·6H₂O
Fuenzalidaite is a very rare, complex potassium, sodium, and magnesium iodate-sulfate, occurring as tiny, hexagonal crystals.
Properties
- Mohs hardness
- 2-3
- Color
- Colourless to pale yellow
- Luster
- Vitreous
- Streak
- White
- Density
- 0
- Cleavage
- possible: fractures || <mi>{11_20}</mi> were observed
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Trigonal
Diagnostic features
## Identification Identification of fuenzalidaite is impossible without advanced laboratory techniques, such as X-ray structural analysis (XRD) or chemical microanalysis (EDS/WDS). In field conditions or in a collection, identification relies on the analysis of the mineral association and the morphology of microscopic, hexagonal crystals on a sample from the type locality. ## Distinguishing from Similar Minerals Fuenzalidaite can be confused with other colorless, secondary nitrate, sulfate, or iodate minerals occurring in the same environment, such as nitratine, darapskite, or brüggenite. Certain differentiation requires specialized analytical studies. ## Crystal Forms It forms very small, hexagonal crystals with prismatic or tabular habits. Crystals often occur as individual specimens or small, loose aggregates on the surface of the host rock.
Geological environment
## Genesis Fuenzalidaite is a secondary mineral, formed in extremely arid (desert) climatic conditions. It crystallizes from solutions rich in iodine, sulfates, sodium, potassium, and magnesium in the weathering zone of Chilean saltpeter (caliche) deposits. ## Mineral Associations This mineral occurs in association with other rare iodates and sulfates. Most commonly, it co-occurs with nitratine, darapskite, brüggenite, and leightonite. The presence of these minerals is a key indicator when searching for fuenzalidaite. ## Localities The only confirmed occurrence of fuenzalidaite in the world is its type locality - the Pampa del Pique mine, Taltal district, in the Antofagasta region of the Atacama Desert in Chile.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a fuenzalidaite specimen primarily depends on the presence of well-formed crystals identifiable under a microscope. The most valuable samples are those where the crystals are clearly visible, undamaged, and occur in a rich association with other rare minerals from that locality. Due to the microscopic nature of the mineral, the size of the entire sample is of secondary importance compared to the quality of the microcrystals themselves. ## Popular Localities The only source of fuenzalidaite specimens is the Pampa del Pique mine in Chile. All samples available on the collector's market come from this single location.
Care and storage
## Cleaning Due to the microscopic size and delicacy of the crystals, mechanical cleaning is inadvisable and practically impossible. Specimens should be protected from dust. ## What to Avoid Contact with water and chemicals should be avoided, as fuenzalidaite, as a mineral from the sulfate and iodate group, may be soluble. It should be protected from high temperatures, humidity, and direct sunlight, which could cause dehydration or decomposition. ## Storage Fuenzalidaite specimens should be stored under stable conditions, preferably in sealed, transparent "micromount" boxes, which protect them from dust, humidity, and mechanical damage.