Sarcolite
Chemical formula: Na₄Ca₁₂Al₈Si₁₂O₄₆(SiO₄,PO₄)(OH,H₂O)₄(CO₃,Cl)
Sarcolite is a rare tectosilicate from the scapolite group, forming vitreous, whitish or flesh-pink crystals with a characteristic square cross-section.
Properties
- Mohs hardness
- 6
- Color
- Flesh-pink, flesh-red, colourless
- Luster
- Vitreous to greasy
- Streak
- White
- Density
- 2.91
- Cleavage
- Imperfect on {001} and {110}
- Fracture
- Conchoidal
- Transparency
- Translucent
- Crystal system
- Tetragonal
Diagnostic features
## Identification The key diagnostic feature of sarcolite is the form of its crystals – short, tetragonal prisms with a square cross-section, often terminated by a bipyramid. The characteristic flesh-pink color, vitreous luster, and occurrence in a specific geological environment (lava blocks of Vesuvius) are also distinctive. ## Differentiation from Similar Minerals Sarcolite can be confused with other silicates of similar color and habit, such as some feldspars or other minerals from the scapolite group. It is distinguished from feldspars by its tetragonal crystallographic system (the crystal cross-section is square, not rectangular). It can be difficult to distinguish from other scapolites without advanced analysis, but the crystal form and mineral associations in its classic locality are very characteristic. ## Crystal Forms Sarcolite crystallizes in the tetragonal system. It forms short, thick prismatic crystals with a square cross-section, terminated by double pyramid faces. The surfaces of the prismatic faces may be striated parallel to the crystallographic axis.
Geological environment
## Genesis Sarcolite is a mineral of metamorphic and metasomatic origin. It forms as a result of high-temperature contact processes. The most famous specimens formed in altered limestone blocks ejected during volcanic eruptions, where hot gases and solutions reacted with carbonate rock. ## Mineral Associations This mineral co-occurs with other minerals typical of skarn environments and volcanic blocks. In its type locality (Monte Somma), it is associated with, among others, vesuvianite, diopside, phlogopite, sanidine, and leucite. ## Localities The most important and historical locality for sarcolite, from which the best specimens originate, is the Somma-Vesuvius volcanic complex in Campania, Italy. This is its type locality. It is also known from several other places in the world, for example, from the Eifel region in Germany, but specimens from there do not match the quality of the Italian ones.
Rarity
Rare
For collectors
## Quality Criteria The most prized specimens by collectors are those from the historical locality of Monte Somma. Key evaluation criteria include: well-formed, sharp, and undamaged crystals with a distinct square cross-section, transparency, and an intense, flesh-pink color. The attractiveness is also enhanced by the placement of crystals on a contrasting rock matrix, accompanied by other rare minerals from this locality. ## Popular Localities By far the most desired and classic locality, from which almost all valuable collector's specimens originate, is the Somma-Vesuvius complex in Italy.
Care and storage
## Cleaning Sarcolite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. It should be dried immediately and thoroughly. ## What to Avoid Contact with acids and other chemicals that can damage the mineral's surface should be avoided. Sarcolite is sensitive to sudden temperature changes. It should not be exposed to prolonged direct sunlight, which can cause color fading. ## Storage It is recommended to store sarcolite in separate, padded boxes or display cases to prevent scratching by harder minerals. Due to its brittleness, it should be protected from impacts and falls.