Zirsinalite
Chemical formula: Na<sub>6</sub>CaZr<sup>4+</sup>Si<sub>6</sub>O<sub>18</sub>
Zirsinalite is a rare sodium, calcium, and zirconium cyclosilicate that rapidly alters to gagarinite-(Y) in air.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 2.93
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification Identification of zirsinalite in field conditions is impossible due to its immediate alteration. Identification requires advanced laboratory methods, such as X-ray diffraction (XRD), performed on freshly collected material under controlled conditions. In collections, it exists exclusively as specimens preserved in liquid or ampoules. ## Distinguishing from Similar Minerals The product of its alteration is gagarinite-(Y), which forms white, chalky coatings or pseudomorphs after zirsinalite. In its unaltered state, within the host rock, it may resemble other colorless, vitreous minerals, but its instability is a unique characteristic. ## Crystal Forms Zirsinalite crystallizes in the trigonal system. It typically forms anhedral (irregular) grains and aggregates up to 1 cm in size, intergrown with the rock. Well-formed crystals are not known.
Geological environment
## Genesis Zirsinalite is a mineral of magmatic origin. It forms in ultra-alkaline (agpaitic) pegmatites and hydrothermal veins associated with nepheline syenite massifs. It crystallizes in the late stages of crystallization in an environment extremely poor in silica and rich in sodium and rare elements. ## Mineral Associations This mineral co-occurs with other rare alkaline minerals, such as eudialyte, lorenzenite, nepheline, microcline, aegirine, lamprophyllite, murmanite, lomonosovite, and villiaumite. ## Localities The most important and classic localities for zirsinalite are in Russia, in the alkaline massifs of the Kola Peninsula: - Khibiny Massif (Koashva Mountain, Nyorkpakhk Mountain) - type locality. - Lovozero Massif (Alluaiv Mountain, Karnasurt Mountain). Outside of Russia, it has also been reported in the Ilimaussaq alkaline complex in Greenland.
Rarity
Very rare
For collectors
## Quality Criteria The quality of a zirsinalite specimen primarily depends on its preservation. The most valuable samples are those that were professionally secured immediately after extraction and remain transparent, immersed in liquid or in an ampoule. The size of the preserved grain or aggregate is also important. Specimens that have undergone partial or complete alteration into white, opaque gagarinite-(Y) have significantly lower value. ## Popular Localities Almost all collector specimens come from two Russian alkaline massifs: Khibiny and Lovozero on the Kola Peninsula. These are the classic and most prized localities for this mineral.
Care and storage
## Cleaning Zirsinalite specimens are not cleaned in the traditional manner. Any contact with water, alcohol, or other liquids leads to its immediate alteration. The mineral must be stored under completely anhydrous conditions. ## What to Avoid Contact with air, moisture, water, and carbon dioxide must be strictly avoided. The mineral is extremely unstable and rapidly undergoes pseudomorphosis (alteration) into gagarinite-(Y) under atmospheric conditions. It should not be heated or exposed to any chemicals. ## Storage The only effective methods for storing zirsinalite are to immerse it in a hermetically sealed container with an anhydrous liquid (e.g., toluene) or in a sealed glass ampoule in an inert gas atmosphere (e.g., argon). "Dry" storage in a box is insufficient and leads to the destruction of the specimen.