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.
Refractive Index 1.619-1.644
Colors Pale to dark green, blackish green, black.
Luster Vitreous, sometimes dull.
Fracture Uneven, Often fibrous nature
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
Dispersion 0.009
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 of Fe).
Absorption Spectrum 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.

Optics α = 1.619-1.622; β = 1.632-1.634; γ = 1.642-1.644 (Tanzanian material). Biaxial (-); 2V = 78°. See chart for series member optics.

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.)