Apatite Crystal with fan-shaped Epidote

In 2021, Gemrock Peru "mined" Epidote and Apatite in the desert mountains of Lima province. They are actually surface collected (Rockhounding). No dynamite or chemicals were used, and no habitat was destroyed.

Apatite:

Apatite is very common as an accessory mineral in igneous and metamorphic rocks, where it is the most common phosphate mineral. However, occurrences are usually as small grains that are often visible only in thin section. Coarsely crystalline apatite is usually rare. In this case, it was found in a skarn rock.

Apatite is the defining mineral for 5 on the Mohs scale. It is often fluorescent under ultraviolet light.

Use as a gemstone:

Apatite is infrequently used as a gemstone. Transparent stones of clean color have been faceted, and chatoyant specimens have been cabochon-cut. In this case, the inside of the white tubular crystals from our extraction is light green, known in gemstone cutting as asparagus stone. Gemrock fabricates Apatite Gemstones from bigger broken crystals.

Epidote:

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 Epidote Crystals:

This rare type of Epidote crystal 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.

Location:

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.

Geological Formation:

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.

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

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