Golyshevite
Chemical formula: Na<sub>10</sub>Ca<sub>9</sub>Zr<sup>4+</sup><sub>3</sub>Fe<sup>2+</sup><sub>2</sub>SiNb<sup>5+</sup>(Si<sub>3</sub>O<sub>9</sub>)<sub>2</sub>(Si<sub>9</sub>O<sub>27</sub>)<sub>2</sub>(OH)<sub>3</sub>(CO<sub>3</sub>)·H<sub>2</sub>O
Golyshevite is an extremely rare mineral from the eudialyte group, a complex zirconosilicate of calcium and sodium, discovered in the Kovdor Massif in Russia.
Properties
- Mohs hardness
- 5
- Luster
- Vitreous
- Streak
- White
- Density
- 3.05
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Transparent to Translucent
- Crystal system
- Trigonal
Diagnostic features
## Identification Amateur identification of golyshevite is practically impossible. A key clue is its origin from the only known locality – the Kovdor Massif. The brownish-yellow color, vitreous luster, and occurrence as granular aggregates in alkaline pegmatites are auxiliary features. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical composition analysis (EDS/WDS). ## Distinguishing from Similar Minerals Golyshevite is visually indistinguishable from many other yellow and brown minerals of the eudialyte group (e.g., eudialyte, kentbrooksite, raslakite). The differences between them lie solely in subtle changes in chemical composition and crystal structure, which can only be detected in a laboratory. ## Crystal Forms Crystals are poorly formed, with a general rhombohedral outline. They usually form granular aggregates where individual crystals are intergrown.
Geological environment
## Genesis Golyshevite forms in a very specific geological environment. It occurs in pegmatite veins cutting through phoscorites and carbonatites within an alkaline-ultrabasic intrusive massif. ## Mineral Associations This mineral co-occurs with other minerals typical of alkaline pegmatites. In its vicinity, one can find aegirine-diopside, pectolite, potassium feldspar, nepheline, titanite, minerals from the apatite group, calcite, and dolomite. ## Localities The only confirmed locality of golyshevite in the world is its type locality: Zhelezny Mine (Железный рудник) in the Kovdor Massif on the Kola Peninsula (Murmansk Oblast, Russia).
Rarity
Extremely rare
For collectors
## Quality Criteria For collectors specializing in rare species, every golyshevite specimen is valuable. Its value increases with the size and quality of crystal development, even if they are imperfect. The intensity and purity of the honey-yellow color also enhance the specimen's attractiveness. Samples with well-visible crystals against a contrasting rock matrix or in association with other rare minerals are particularly prized. ## Popular Localities All specimens available on the collector's market come from a single location in the world – the Kovdor Massif in Russia. This is the only source of this mineral.
Care and storage
## Cleaning Specimens should only be cleaned mechanically, using a soft brush to remove dust. For heavier dirt, distilled water can be used. Ultrasonic cleaners should be avoided, as they can cause cracks in brittle crystals. ## What to Avoid As a complex silicate containing carbonate and hydroxyl groups, the mineral is susceptible to acids, which can damage or completely destroy it. It should be protected from contact with chemicals. Rapid temperature changes are also recommended to be avoided. ## Storage Store in separate, sealed display boxes to prevent dusting and scratching by harder minerals. It does not require special conditions regarding humidity or lighting, but it is generally recommended to protect it from prolonged exposure to strong sunlight.