Schorlomite Garnet and Nepheline (Nephelite) Schorlomite Garnet. Crystal system: Cubic. Hardness 6.5 to 7.5. Luster Vitreous. Chemical formula: Ca3Fe2 (SiO4)3. Garnets belong to the nesosilicate group. Titaniferous variety of Andradite, comes from alkaline rocks. Nepheline: Hardness: 5 1/2-6. Luster: vitreous, greasy. Crystal system: hexagonal. Feldspathoid family with silica framework Add to basket