Facts
- Chemical formula
- Al₂SiO₄F₂
- Crystal system
- Orthorhombic
- Mohs hardness
- 8.0
- Density
- 3.53 g/cm³
- Number of elements
- 4
- IMA status
- Grandfathered
- Named after
- St. John's Island, Egypt
Sources: Wikidata (CC0), IMA list of minerals via Wikidata · Wikidata Q134985