Stronalsite
Chemical formula: Na<sub>2</sub>SrAl<sub>4</sub>Si<sub>4</sub>O<sub>16</sub>
Stronalsite is a rare sodium, strontium, and aluminum silicate, forming colorless to white, tabular crystals with a vitreous luster.
Properties
- Mohs hardness
- 6
- Luster
- Vitreous
- Streak
- White
- Density
- 2.88
- Cleavage
- Perfect on {010} and {001}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Stronalsite is difficult to identify visually without specialized equipment. It is recognized by its crystal form (small, tabular), perfect cleavage in two directions, and occurrence environment. Certain identification requires advanced methods, such as chemical analysis (EDS) or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other white feldspars or zeolites, with which it often co-occurs. It is distinguished from feldspars (e.g., anorthite, with which it forms a series) by the presence of strontium in its chemical composition. It differs from zeolites by slightly higher hardness and specific cleavage angles. ## Crystal Forms Stronalsite crystals are usually very small, with a tabular or bladed habit. It crystallizes in the orthorhombic system. It often forms twinning, which is characteristic of feldspars.
Geological environment
## Genesis Stronalsite is a metamorphic mineral. It forms as a result of high-grade contact metamorphism (sanidinite facies) within aluminum-rich sedimentary rock xenoliths in volcanic rocks, such as dacites. ## Mineral Associations This mineral co-occurs with other high-temperature minerals. It is most often accompanied by anorthite, cordierite, sillimanite, corundum, spinel, osumilite, and siliceous glass. ## Localities The most important and well-documented stronalsite localities worldwide include: - Japan - Shionomachi mine in Ehime Prefecture (type locality) and Tadano, Fukushima Prefecture. - Germany - the Laacher See region in the Eifel mountains, Rhineland-Palatinate, where it occurs in xenoliths within volcanic tuffs.
Rarity
Very rare
For collectors
## Quality Criteria The quality of stronalsite specimens is primarily assessed based on crystal development and size. Specimens with distinct, well-formed, even if small, crystals embedded in a contrasting rock matrix are most valued. Due to its rarity, every well-identified specimen has value for specialized collectors. ## Popular Localities The most well-known specimens, though microscopic in size, come from the volcanic Eifel region in Germany. Material from the type locality in Japan is extremely rare in collections.
Care and storage
## Cleaning Stronalsite 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 strong chemicals, which can damage the mineral's surface, should be avoided. Due to its perfect cleavage, it is susceptible to impact and mechanical pressure. It should not be cleaned in ultrasonic cleaners. ## Storage Stronalsite specimens are best stored in separate, padded display boxes to protect them from scratches and mechanical damage. It should be protected from dust and sudden temperature changes.