Friedelite Value, Price, and Jewelry Information

Mixed cushion-cut friedelite, 2.97 cts, 10 x 8 mm, Franklin, New Jersey. © The Gem Trader. Used with permission.

Friedelite

Friedelite is not abundant, and gem-quality material is rarely seen even in large collections. Faceted gems are true collector’s items.

Friedelite Information

Data Value
Name Friedelite
Colors Pale pink to dark brownish red, red, brown, orange-red.
Crystallography Monoclinic. Crystals are tabular, needlelike, hemimorphic, and very rare. Usually massive, fibrous aggregates, cryptocrystalline.
Refractive Index 1.625-1.664
Luster Vitreous.
Hardness 4-5
Fracture Uneven
Specific Gravity 3.04-3.07
Birefringence 0.030
Cleavage Perfect 1 direction
Luminescence May be reddish in LW and SW; some material green (SW) and yellow (LW).
Luminescence Present Yes
Luminescence Type Fluorescent, UV-Long, UV-Short
Transparency Translucent to opaque.
Absorption Spectrum Broad band at 5560 and also 4560 (indistinct); spectrum not diagnostic.
Formula

(Mn, Fe)8Si6O18(OH, CI)· 3H2O

Optics

o = 1.654-1.664; e = 1.625-1.629. Uniaxial (-).

Optic Sign Uniaxial -
Etymology

Named after the French chemist and mineralogist, Charles Friedel.

Occurrence

In manganese deposits.

friedelite on matrix

This 4 x 3 cm carpet of friedelites on a matrix of franklinite, calcite, and willemite contains individual crystals that measure just over 1 mm in size. Sterling Mine, Sterling Hill, Ogdensburg, Franklin Mining District, Sussex Co., New Jersey, USA. © Rob Lavinsky, www.iRocks.com. Used with permission.

Comments

Lovely friedelite cabochons cut from Franklin, New Jersey material show rich, brownish red colors, while cabs cut from material from the deep manganese mine at Kuruman, South Africa show rose-red colors. Cut stones from both these locations are usually translucent. However, gem cutters have faceted very little of this material.

Friedelite belongs to the pyrosmalite mineral group, which includes schallerite and pyrosmalite.

Identifying Characteristics

Refractometer readings usually show a shadow edge at about 1.645.

Synthetics

No known synthetics.

Sources

Franklin, New Jersey produces gem-quality material, typically brownish and cryptocrystalline, that looks like fibrous chalcedony. Seams of the material at this deposit range up to 2 inches wide. Most gem-quality friedelites come from this location.

Kuruman, South Africa produces massive, dark rose-red material.

Other notable sources of this mineral include the following:

  • Austria; Adervielle, France; Kazahkstan; Orebro, Sweden.

Stone Sizes

Translucent stones can normally range up to 1 to 5 carats in size. Although cabochons can be cut to about 30 x 40 mm, larger stones lose any transparency.

Care

You’re more likely to find friedelites, if at all, in mineral collections than in jewelry collections. These gems have significantly lower hardness (4-5) than more common jewelry stones. So, store them separately from other gems to avoid contact scratches. Use protective settings for ring wear. However, necklace and earring use should pose fewer risks. Clean these gems only with a soft brush, mild detergent, and warm water. Consult our gemstone jewelry cleaning guide for more recommendations.

faceted friedelite - New Jersey

Friedelite: Franklin, New Jersey (1.74). Photo © Joel E. Arem, PhD, FGA. Used with permission.

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