Physical Properties |
|
| Chemical formula | Ca2(Al,Fe)3Si3O12(OH) |
| Class | Sorosilicate Paired tetrahedra groups |
| Crystal system | Monoclinic |
| Habit | Prismatic Fibrous Acicular Granular Massive Fibrous aggregates |
| Color | Pistachio green Yellow-green to black |
| Hardness | 6 to 7 |
| Specific gravity | 3.4 to 3.5 |
| Cleavage | Perfect (001), poor (100) |
| Fracture | Uneven |
| Luster | Vitreous |
| Transparency | Transparent to translucent |
| Streak | White |
Optical Properties |
|
| PPL | Usually colorless; may be light green or pink, depending on composition Typically non-pleochroic High relief |
| XPL | Up to 3rd order colors with increasing Fe content Football-shaped Concentric color rings |
| δ | 0.01 |
| after Perkins, 350 |
Epidote in Hand Sample
Epidote in unakite
Epidote in a different unakite
Epidote in Catoctin Formation metabasalt
Epidote-family mineral zoisite, with black hornblende and red corundum (ruby)
Epidote marking a fault contact between two gneisses
Epidote in Thin Section
Thin Section GigaPans
Epidote in epidosite, plane polars
Epidote in epidosite, crossed polars
Epidote in unakite, plane polars
Epidote in unakite, crossed polars
Epidote, Plane Polars
Epidote in plane polarized light. Magnification: 100x Rock: Epidosite Click here to watch this grain rotate in crossed polars: https://youtu.be/dMUWtYZJM2o C…
Epidote, Crossed Polars
Epidote in cross polarized light. Magnification: 100x Rock: Epidosite Click here to watch this grain rotate in plane polars: https://youtu.be/ngcacHsI7mY Cli…
Epidote in Unakite, Plane Polars
Epidote in plane polarized light. Magnification: 40x Rock: Unakite Click here to watch epidote rotate in crossed polars: https://youtu.be/uv6CqsF99C8 Click h…
Epidote in Unakite, Crossed Polars
Epidote in cross polarized light. Magnification: 40x Rock: Unakite Click here to watch epidote rotate in plane polars: https://youtu.be/RD38DloUmqs Click her…
The preceding pictures and videos are of epidote in epidosite and unakite, where it’s quite easy to spot. You’re more likely to encounter epidote as a tiny, easily overlooked accessory mineral; the following pictures and videos are of tiny, easily overlooked accessory epidote.
Epidote, Plane Polars
Epidote in plane polars, showing high relief. Magnification: 100x To see this grain in crossed polars, click here: https://youtu.be/Qaa1msEEh9w To see epidot…
Epidote, Crossed Polars
Epidote in crossed polars, showing high relief and moderate birefringence. Magnification: 100x To see this grain in PPL, click here: https://youtu.be/f0zJweq…
Chlorite with Epidote Grains, Plane Polars
Two large chlorite grains peppered with epidote grains in plane polarized light. Magnification: 40x Rock: Metagranodiorite Click here to watch these grains r…
Chlorite with Epidote Grains, Crossed Polars
Two large chlorite grains peppered with epidote grains in cross polarized light. Magnification: 40x Rock: Metagranodiorite Click here to watch these grains r…