Apophyllite-(KF)
KCa4Si8O20F • 8H2O [CNMNC approved formula]
Named from the Greek apophylliso - "it flakes off." and the composition containing fluorine;.
| IMA status : | Renamed IMA Approved; 2008 (IMA1976-001) |
| CLASSIFICATION | |
| Dana (8th edition) : |
72.03.01.01 |
| (72) Phyllosilicate Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings | |
| (72.03) with 3-, 4-, or 5-membered rings and 8-membered rings | |
| (72.03.01) Apophyllite group (4- & 8-membered rings) | |
| Nickel-Strunz (10th edition) : |
09.EA.15 |
| (09) Silicates | |
| (09.E) Phyllosilicates | |
| (09.EA) Single nets of tetrahedra with 4-, 5-, (6-), and 8-membered rings | |
| Crystal system: | Tetragonal System |
| Point group (H-M): | 4/mmm (or 4/m 2/m 2/m) — ditetragonal-dipyramidal |
| Unit cell: | a = 8.963(2) Å, c = 15.804(2) Å |
| Crystal Habit: | Crystalline; Massive ; Pseudo Cubic |
| Color: | Colorless, pale green, aquamarine, white, pink, yellow |
| Diaphaneity: | Transparent, Translucent |
| Luster: | Vitreous, Pearly |
| Hardness (Mohs): | 4.5 - 5 |
| Measured Density: | 2.33 - 2.37 g/cm3 |
| Cleavage: | 2; Perfect on {001}, Imperfect on {110} |
| Tenacity: | Brittle |
| Fracture: | Irregular/Uneven |
| Streak: | White |
| Geologic Setting: | A secondary mineral in amygdules or druses in basalts. A late-stage mineral in some mineral deposits. |
| Synonyms/varieties: | Fluorapophyllite |
| Other Properties: | Gemstone Extremely Rare. |
| Comments: | IMA approved 1976 as Fluorapophyllite. Renamed to Apophyllite-(KF) in 2008. |
Doubly terminated, very clear and perfect Apophyllite-(KF) with white stilbite.Origin: Jalgaon, India.
Sample size: 4 x 3.5 cm
Photo: © Fabre Minerals