| Agrellite | |
| Category: | Inosilicates |
| Formula: | NaCa2Si4O10F |
| Imasymbol: | Are[1] |
| Strunz: | 9.DH.75 |
| System: | Triclinic |
| Class: | Pinacoidal (same H-M symbol) |
| Symmetry: | P |
| Color: | White, grayish-white, greenish-white |
| Habit: | Lath - shaped like a small, thin plaster lath, rectangular in shape |
| Cleavage: | perfect [110] |
| Mohs: | 5.5 |
| Luster: | pearly |
| Refractive: | nα = 1.567 nβ = 1.579 nγ = 1.581 |
| Opticalprop: | biaxial |
| Birefringence: | δ = 0.014 |
| Streak: | white |
| Gravity: | 2.88 |
| Diaphaneity: | translucent |
| References: | [2] [3] |
Agrellite (NaCa2Si4O10F) is a rare triclinic inosilicate mineral with four-periodic single chains of silica tetrahedra.
It is a white to grey translucent mineral, with a pearly luster and white streak. It has a Mohs hardness of 5.5 and a specific gravity of 2.8. Its type locality is the Kipawa Alkaline Complex, Quebec, Canada, where it occurs as tabular laths in pegmatite lenses.[4] Other localities include Murmansk Oblast, Russia, Dara-i-Pioz Glacier, Tajikistan, and Saima Complex, Liaoning, China. Common associates at the type locality include zircon, eudialyte, vlasovite, miserite, mosandrite-(Ce), and calcite.
Agrellite displays pink fluorescence strongly under shortwave and weakly under longwave ultraviolet light.[5] [6] The fluorescent activator is dominantly Mn2+, with minor Eu2+, Sm3+, and Dy3+.
It is named in honor of Stuart Olof Agrell (1913–1996), a British mineralogist at Cambridge University.