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A beautiful and rare stand-alone Epidote crystal fan from Gemrocks Crystal rockhounding/mining area in the District San Antonio de Chaclla, near Peru’s capital, Lima.
Rarity:
Normally, Epidote forms crystals in the monoclinic system. Fan-shaped crystals are rare and known only from a handful of locations in the USA, Pakistan, and Peru. Most specimens sold nowadays originate from Pakistan and an area north of Lima, in Peru.
In 2021, Gemrock Peru "mined" Epidote in the desert mountains of Lima province. They are actually surface collected (Rockhounding). The area is located in the Andean foothills east of Lima at about 2400 meters of altitude. The Epidote fans of this area have a different aspect than the Pakistani and other Peruvian Epidote fans in the sense that their coloring is a lighter green, and the structure of the fans is finer and more detailed. Each fan is formed by several very thin layers. In that sense, the fans from this location are unique. In over six months of daily rockhounding in the area, we could only produce a few hundred specimens, and of those,e only a few dozen pieces are nice stand-alone fans, which makes those pieces very unique and rare.
The location is a new location for those crystals.
Eco-friendly mining:
The specimens are surface collected (Rockhounding). No dynamite or chemicals were used, and no habitat was destroyed. No permanent mining camp was constructed. Trash was collected at the campsite and transported regularly out of the area. Our operation was of such little disturbance that we had an endangered mountain puma walking through the tents at night.
Ethical Mining:
The rockhounding operation did count on the permit and coordination of the legal mining concession holder. The staff of Gemrock is hired under formal labor contracts with all legally required labor benefits.
Epidote Geology:
Epidote is an abundant rock-forming mineral, but it is of secondary origin. It occurs in marble and schistose rocks of metamorphic origin. It is also a product of hydrothermal alteration of various minerals (feldspars, micas, pyroxenes, amphiboles, garnets, and others) composing igneous rocks.
Many of the characteristics of the mineral vary with the amount of iron present, for instance, the color, the optical constants, and the specific gravity. The color is green, grey, brown, or nearly black, but usually a characteristic shade of yellowish-green or pistachio-green.
Well-developed crystals of epidote are crystallizing in the monoclinic system and are of frequent occurrence: they are commonly prismatic in habit, the direction of elongation being perpendicular to the single plane of symmetry. The faces are often deeply striated, and crystals are often twinned.
Fan-shaped crystals are a rare type of Epidote crystal that is only known from a few places in the USA, Pakistan, and Peru. These crystals are looking like thin layers of fibers that are organized in a fan-like structure, starting at a central point and then fanning out.
The area where this crystal was collected is located in the Andean Foothills to the east of Peru’s capital Lima, at an altitude of approximately 2400 meters. The area is a skarn area.
Most skarns form when carbonate rocks such as limestone, dolostone, or marble are intruded by a magma body and altered by contact metamorphism and metasomatism. At the time of intrusion, the heat of contact metamorphism is the primary agent of change.
Then, as the magma cools, it releases hot, acidic, silicate-rich fluids. When this water is expelled from the magma, it is a solvent that has the ability to carry heat and chemically active solutes into the country rock. The water leaving the magma moves through the surrounding rock by flowing or diffusing through pore spaces, fractures, and even the mineral grains that make up the rock. As it invades carbonate rock, the hot, acidic, metal-laden water dissolves, replaces, recrystallizes, and alters minerals in the carbonate rock. These acidic waters are superheated and supersaturated with dissolved metal ions, especially calcium and silicon. As the acidic water moves through the carbonate rocks, its temperature falls and its acidity is neutralized.
Learn more about Epidote Geology.
Optical characteristics
Epidote displays strong pleochroism (or iridescence), which means its optical properties vary with the direction of light. The direction of the electric field determines the polarization of light, and crystals will respond in different ways if this angle is changed.
Iridescent Epidote cabochons
The fan-shaped crystal clusters often occur in a more solid state that is not very attractive for crystal specimen collectors. These clusters, however, can be used for gem cutting. Given the microscopic structure of these clusters, the resulting cabochons do show a fascinating effect of iridescence when moved