Chromio-pargasite
Chemical formula: NaCa<sub>2</sub>(Mg<sub>4</sub>Cr<sup>3+</sup>)(Si<sub>6</sub>Al<sub>2</sub>)O<sub>22</sub>(OH)<sub>2</sub>
A silicate from the amphibole group, a chromium analog of pargasite, characterized by an intense green color.
Properties
- Mohs hardness
- 6
- Luster
- Vitreous
- Streak
- Light green
- Density
- 3.1-3.2
- Cleavage
- Good on {110}
- Fracture
- Uneven
- Transparency
- Translucent to Opaque
- Crystal system
- Monoclinic
Diagnostic features
## Identification The most important diagnostic feature of chromio-pargasite is its intensely green color combined with the typical prismatic habit of amphiboles and characteristic cleavage. Vitreous luster and relatively high hardness are also helpful in identification. ## Distinguishing from similar minerals Chromio-pargasite can be confused with other green minerals: - **Chromian diopside**: has a very similar color but different cleavage (two planes at an angle close to 90°). - **Actinolite**: usually forms fibrous or acicular aggregates and rarely has such an intensely emerald color. - **Uvarovite (garnet)**: has a similar color but crystallizes in the isometric system (usually as small, shiny dodecahedra) and does not exhibit cleavage. - **Chromian tourmaline**: has a different crystal habit (prismatic with characteristic transverse striations on the faces) and does not have cleavage. Final and certain differentiation from other chromian amphiboles requires advanced chemical analysis (e.g., EDS). ## Crystal forms Crystals are usually columnar or prismatic, often terminated by simple faces. It also occurs as granular, radial, or embedded aggregates in the host rock.
Geological environment
## Genesis Chromio-pargasite is a metamorphic rock mineral. It forms under conditions of high-grade metamorphism, in a chromium-rich environment. Its presence is usually associated with altered ultramafic rocks (e.g., serpentinites, peridotites) or skarns in contact with such rocks. ## Mineral associations This mineral often co-occurs with other minerals typical of chromium-bearing rocks, such as chromite, chromian diopside, tremolite, serpentine, talc, uvarovite, as well as calcite and dolomite. ## Localities The most important global localities from which well-formed chromio-pargasite specimens originate include: - Kop Krom Mine in Erzurum Province, Turkey. - Outokumpu region in Finland. - Saranovskii Mine in the Urals, Russia.
Rarity
Rare
For collectors
## Quality criteria The most desirable specimens for collectors are those with well-formed, undamaged crystals of intense, emerald-green color. Crystals exhibiting transparency, which is rare, are highly valued. The attractiveness of a specimen is also enhanced by its aesthetic placement on a light rock matrix (e.g., on white calcite), which creates a striking contrast. ## Popular localities The deposits in Turkey (Kop Krom) are considered the best source of collector specimens, providing large, well-formed crystals of excellent color. Specimens from Finland are also valued, although they are often smaller in size.
Care and storage
## Cleaning Chromio-pargasite specimens can be safely cleaned with lukewarm water using a soft brush. Strong detergents should be avoided. After cleaning, the specimen should be thoroughly dried. ## What to avoid The mineral is sensitive to strong acids. It should not be subjected to sudden temperature changes or cleaned in ultrasonic cleaners, as internal stresses can cause cracks. Despite a hardness of 6 on the Mohs scale, it should be protected from contact with harder minerals (e.g., quartz, beryl) to avoid scratches. ## Storage It is recommended to store specimens in separate, padded boxes or in collector's display cases to prevent abrasions and mechanical damage. It is not sensitive to sunlight.