Actinolite Value, Price, and Jewelry Information

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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

Data	Value
Name	Actinolite
Varieties	Smaragdite
Colors	Pale to dark green, blackish green, black.
Hardness	5.5
Fracture	Uneven, Often fibrous nature
Cleavage	2 directions good
Stone Sizes	Actinolite 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)
Formula	Ca₂(Mg, Fe)₅Si₈O₂₂(OH)₂
Crystallography	Monoclinic; bladed crystals, usually elongated; fibrous, columnar aggregates. Also massive, granular, Often twinned.
Refractive Index	1.619-1.644
Birefringence	0.022-0.026.
Dispersion	0.009
Luminescence	None (due to presence of Fe).
Absorption Spectrum	Faint line at 5030.
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.
Optic Sign	Biaxial -
Luminescence Present	No
Luster	Vitreous, sometimes dull.
Specific Gravity	Usually 3.05; Tanzania: 3.03-3.07; Max.: 3.44.
Transparency	Translucent to transparent.
Phenomena	Chatoyancy.

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.

Chester, Vermont.

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

Tanzania: transparent crystals. (See also nephrite.)