Actinolite Value, Price, and Jewelry Information

Actinolite
Actinolite

Actinolite is a member of a series that contains varying amounts of iron and magnesium. Tremolite is the Mg end, and ferroactinolite the Fe end, with actinolite in the middle. Actinolites with more than 50% Fe are very rare. Catseye actinolite exists (S.G. 3.0, R.I. 1.63); when chatoyant material is cut, it exhibits a fine eye. Actinolite is easy to cleave and hard to cut and would make a poor jewelry stone. Actinolite is the chief constituent of nephrite (jade). Smaragdite is a chrome-rich tremolite from Tanzania.

Actinolite Value

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Actinolite Information

DataValue
NameActinolite
VarietiesSmaragdite
Crystallography Monoclinic; bladed crystals, usually elongated; fibrous, columnar aggregates. Also massive, granular, Often twinned.
Colors Pale to dark green, blackish green, black.
Luster Vitreous, sometimes dull.
Fracture Uneven. Often fibrous nature. Brittle. Compact variety tough.
Hardness 5.5
Specific Gravity Usually 3.05; Tanzania: 3.03-3.07; Max.: 3.44.
Birefringence 0.022-0.026.
Cleavage 2 directions good.
Stone SizesActinolite is rarely facetable and usually in small fragments. Material from Chester, Vermont, could provide stones to about 10 carats. DG: 2.06 (greenish, step cut, Africa)
Luminescence None (due to presence or Fe).
Spectral Faint line at 5030.
FormulaCa2(Mg, Fe)5Si8O22(OH)2
Pleochroism 

Yellow to dark green. Material transparent to nearly opaque. α: pale yellow/ yellowish-green. β: pale yellow-green/green. γ: pale green/ deep greenish blue.

Comments: Actinolite is a member of a series that contains varying amounts of iron and magnesium. Tremolite is the Mg end, and ferroactinolite the Fe end, with actinolite in the middle. Actinolites with more than 50% Fe are very rare. Catseye actinolite exists (S.G. 3.0, R.I. 1.63); when chatoyant material is cut, it exhibits a fine eye. Actinolite is easy to cleave and hard to cut and would make a poor jewelry stone. Actinolite is the chief constituent of nephrite (jade). Smaragdite is a chrome-rich tremolite from Tanzania.

Name: Greek aktis, meaning ray, due to the fibrous nature.

Optics:

α = 1.619-1.622;

β = 1.632-1.634;

γ = 1.642-1.644 (Tanzanian material).

Biaxial (-); 2V = 78°

Occurrence: Contact metamorphic limestones and dolomites; magnesium-rich limestones and ultrabasic rocks; regionally metamorphosed rocks.

Locality Pleochroic Colors α β γ Birefringence S.G. Comments
Fowler, New York red-violet 1.602 – 1.630 0.028 3.03 Hexagonite
Kenya bright green 1.602 1.613 1.628 0.026 2.99 Tremolite
1.607 1.618 1.632 0.025 3.01
Tanzania (Lelatema) yellow green/green 1.608 1.616 1.631 0.023 3.01 Tremolite
Tanzania emerald green 1.611 1.623 1.639 0.028 3.30 Tremolite + Cr
Tanzania (Merelani) yellow-green/emerald green 1.608 1.618 1.63 0.022 Smaragdite
Taiwan yellow-green/green tones, 1.607- – 1.630- 0.023- 3.01 Tremolite
also brownish 1.609 1.633 0.024
1.615- – 1.631- 0.014- 3.01 Catseye tremolite
1.619 1.633 0.016
Uganda yellow-green/green 1.619- 1.632- 1.642- 0.021- 3.04- Tremolite-Actinolite
1.622 1.634 1.644 0.024 3.07
green/brown 1.633 – 1.653 0.020 3.15 Actinolite
Chemical composition vs. optics and density of common hornblendes. Adapted from W.A. Deere, R.A. Howie, and J. Zussman, 1962, The Rock Forming Minerals, vol.2 (New York: Wiley), p.296.
Chemical composition vs. optics and density of common hornblendes.
Adapted from W.A. Deere, R.A. Howie, and J. Zussman, 1962, The Rock Forming Minerals, vol.2 (New York: Wiley), p.296.

Chester, Vermont.

Madagascar: small, dark green crystals. Many of these are clean and suitable for faceting.

Tanzania: transparent crystals. (See also nephrite.)