Actinolite
Actinolite is a silicate mineral recognized among collectors for its crystal form and distribution, with several world-class Chinese localities.
About Actinolite
Actinolite is classified as a silicate mineral in the amphibole group (calcium amphibole — actinolite-tremolite series) and has the chemical formula □Ca2(Mg4.5-2.5Fe0.5-2.5)Si8O22(OH)2. It crystallizes in the monoclinic system and holds a steady position among silicate species. Its combination of structural character and global distribution make it a recognized species in both systematic and aesthetic collections.
Identification & care
Actinolite typically forms bladed, prismatic crystals; fibrous and asbestiform; massive, radiating columnar; compact (smaragdite). Its color is typically bright green to dark green and bluish-green. The luster is vitreous, silky (fibrous), the streak is white, and specimens range from transparent to opaque. The cleavage is perfect on {110} at ~56° and 124° (amphibole cleavage). The fracture is uneven, splintery, which aids identification.
Collector context
How it forms
In terms of geology, Actinolite forms in metamorphic rocks in the greenschist facies (the 'actinolite zone' of progressive metamorphism); also in altered mafic rocks (ophiolites, greenstone belts); blueschist-facies glaucophane-actinolite assemblages. It is commonly found in association with chlorite, epidote, albite, tremolite, talc, magnetite, serpentine.
Classic Chinese localities
**Huanggang Fe-Sn deposit** is an important Chinese source for the species.
Why collectors care
Collectors pursue Actinolite for the clarity of its crystal form and, in good material, saturated color that reads instantly across a display case. A well-terminated actinolite on clean matrix photographs well, identifies quickly, and anchors a cabinet piece. Top Chinese specimens over the last two decades have reset the bar for what actinolite looks like at collector grade.
What affects value
Value in Actinolite is assessed, in typical order of weight, against: (1) locality provenance; (2) size relative to the species norm; (3) crystal form and termination sharpness; (4) color saturation and zoning; (5) transparency and internal clarity; (6) matrix quality and aesthetic balance; (7) condition (absence of damage, chips, or repair). Cleaning quality and verified locality documentation act as multipliers across the above.
Naming history
The name Actinolite has a specific etymological and historical context — see Mindat's reference entry for provenance details. We have retained naming data at the record level; published prose is paraphrased from factual fields rather than copied from source.