4.74 ct ANTHOPHYLLITE – USA

Anthophyllite

Anthophyllite is a gemstone that speaks of the deep, ancient metamorphism of the Earth’s crust. An iron-magnesium amphibole, it is a mineral I have always respected for its “fibrous” soul and its subtle, earthy elegance. While it is often found in massive, rock-forming layers, the rare, gem-quality crystals are a collector’s prize. I am particularly drawn to its “clove-brown” to emerald-green hues, which possess a sub-vitreous to pearly luster. For the specialist, Anthophyllite is a masterclass in polymorphism—it shares a nearly identical chemistry with Enstatite but chooses a completely different structural path. It is a stone of resilience and grounding, offering a “silky” internal texture that makes it look like petrified wood or raw silk frozen in stone.

The Heritage & Discovery

Historical Significance: Anthophyllite holds a significant place in the study of metamorphic geology. Historically, it was one of the first minerals used to define the “amphibole” group, representing the ortho-amphibole branch. It typically forms in high-temperature environments where magnesium-rich rocks, like peridotites, are subjected to intense regional metamorphism. In the world of fine minerals, it is celebrated for its “acicular” (needle-like) and bladed habits. It stands as a symbol of the structural complexity that can arise when magnesium and iron are forged under the immense weight of mountains, bridging the gap between common silicates and the elite world of rare crystals.

Discovery: The mineral was first described in 1801 by the German mineralogist Christian Friedrich Schumacher. Its name is derived from the Latin anthophyllum, meaning “clove,” a direct reference to its characteristic clove-brown color. Scientifically, it is a magnesium iron silicate hydroxide. Its discovery in Kongsberg, Norway, provided mineralogists with the first clear look at the orthorhombic amphiboles, helping to map the vast and complicated family tree of the silicate minerals.

Important Mines: The legendary and type-locality for world-class Anthophyllite is Kongsberg, Norway. I also have a high regard for the spectacular, bladed crystals found in the Hermannov region of the Czech Republic and the rare, gemmy material from Tanzania. For the vault, I prioritize the Norwegian specimens for their historic pedigree and the Tanzanian “clove-colored” crystals for their exceptional transparency and pearly brilliance.

Mineralogical Profile

Description: Anthophyllite is a magnesium iron silicate hydroxide that crystallizes in the orthorhombic system. It sits at a 5.5 to 6 on the Mohs scale, making it a relatively durable mineral, though its fibrous nature can make it prone to splintering if handled roughly. It is characterized by its vitreous to pearly luster and its range of brownish, yellowish, and greenish colors.

One of its most identifying traits is its perfect prismatic cleavage at angles of approximately 54° and 126°, which is the hallmark of the amphibole group. It has a moderate refractive index (approx 1.60 to 1.67) and a distinct pleochroism, often showing different shades of brown or green depending on the viewing angle. Because it is an ortho-amphibole, it lacks the monoclinic “tilt” of more common minerals like Hornblende. When I select a piece for the collection, I look for “fresh,” unweathered blades with a high-gloss luster, as these highlight the sophisticated, three-dimensional geometry that makes Anthophyllite a refined treasure for the systematic collector. It is a dense, “woody” mineral that offers a unique tactile and visual depth unlike any other silicate.

Chemical Formula: (Mg,Fe²⁺)₇Si₈O₂₂(OH)₂