Ferro-actinolite
A variety of Calcium Amphibole Subgroup
What is Ferro-actinolite?
Ferro-actinolite is the ferrous iron-rich endmember of the actinolite-tremolite continuous solid solution series of the double chain calcareous amphibole group of inosilicate minerals. All the series members belong to the monoclinic crystal system. The following formula comparison indicates the position of individual well-known members within the series: tremolite: ☐Ca2(Mg5.0-4.5Fe0.0-0.5)Si8O22(OH)2 actinolite: ☐Ca2(Mg4.5-2.5Fe0.5-2.5)Si8O22(OH)2 ferro-actinolite: ☐Ca2(Mg2.5-0.0Fe2.5-5.0)Si8O22(OH)2 Some other substitute cations that may replace either Ca, Mg, or Fe include potassium (K), aluminium (Al), manganese (Mn), titanium (Ti), and chromium (Cr). A fluorine (F) anion may partially replace the hydroxyl (OH).
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Ferro-actinolite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Ferro-actinolite Localities Map
See where Ferro-actinolite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Key Characteristics
Characteristics of Ferro-actinolite
Ferroactinolite prisms are much darker in color than actinolite due to their higher iron content affecting opacity, but may be dark green in thin slices or around the edges. Its crystals are brittle, with a hardness of 5-6 on the Mohs scale, and have a white streak. Ferroactinolite is pleochroic and has a higher refractive index and surface relief than actinolite.
Quick Facts
Physical Properties
- Color
- black-green, dark green
- Hardness (Mohs)
- 5 - 6
- Streak
- greenish white
Chemical Properties
- Chemical Formula
- ☐{Ca2}{Fe2+5}(Si8O22)(OH)2
- Elements
- Ca, Fe, H, O, Si
Also Known As
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Ferro-actinolite FAQs
How do I identify Ferro-actinolite?
Ferro-actinolite can be identified by its hardness of 5 - 6 on the Mohs scale, black-green color. Look for these key characteristics when examining specimens.
What color is Ferro-actinolite?
Ferro-actinolite typically appears in black-green, dark green. Color can vary depending on impurities and formation conditions.
How hard is Ferro-actinolite?
Ferro-actinolite has a hardness of 5 - 6 on the Mohs scale. This gives it moderate hardness.
What is the characteristics of ferro-actinolite of Ferro-actinolite?
Ferroactinolite prisms are much darker in color than actinolite due to their higher iron content affecting opacity, but may be dark green in thin slices or around the edges. Its crystals are brittle, with a hardness of 5-6 on the Mohs scale, and have a white streak. Ferroactinolite is pleochroic and has a higher refractive index and surface relief than actinolite.
