Epidote Value, Price, and Jewelry Information


epidote - Madagascar
“Cut Epidote,” Madagascar, 1.86 cts, by Didier Descouens. Licensed under CC By-SA 4.0.

The epidote mineral supergroup contains many related species of interest to collectors. However, epidote itself is the one most likely to be faceted into beautiful, albeit small and dark, gemstones.

Epidote Value

Highest values go to transparency, color, and size.

The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

Epidote Value via Gem Price Guide
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Epidote Information

DataValue
NameEpidote
Crystallography All are monoclinic. Crystals prismatic and tabular; also granular, massive, fibrous; sometimes twinned, often striated.
Colors Epidote shows shades of green, yellow, gray, grayish white, greenish black, black; usually very dark. Clinozoisite is colorless, pale yellow, gray, green, pink; often zoned. Piedmontite is reddish brown, black, rose red, pink. Allanite is light brown to black. Hancockite is brownish or black.
Luster Vitreous; pearly on cleavages; massive materials dull. Allanite resinous, pitchy.
Polish Luster Vitreous to greasy, allanite resinous
Fracture Luster Vitreous, pearly, dull
Fracture Conchoidal to uneven; brittle.
Hardness 6-7. Epidote sometimes slightly harder, piedmontite softer.
Toughness Fair to poor
Specific Gravity See "Identifying Characteristics" below.
Birefringence See "Identifying Characteristics" below.
Cleavage Perfect 1 direction in all.
Dispersion 0.030
Heat SensitivityYes
Luminescence Usually none.
Transparency Transparent to Opaque
UV LongUsually inert, not diagnostic
UV ShortUsually inert, not diagnostic
Absorption Spectrum Most members of the group have non-diagnostic spectra. Epidote has a very strong line at 455 nm. Sometimes, a weak line is seen at 475 nm. This spectrum is very sensitive to direction within the material and isn't visible in certain orientations.
Phenomena Chatoyancy, very rare. (Epidote and clinozoisite).
FormulaThe general formula of the epidote group is X2Y3Z3(O,OH,F)13 where X = Ca, Ce, La, Y, Th, Fe, Mn; Y = Al, Fe, Mn, Ti; Z=Si, Be.
  • Clinozoisite: Ca2Al3Si3O12(OH)
  • Epidote: Ca2(Al,Fe)3Si3O12(OH)
  • Piedmontite: Ca2(Mn,Fe,Al)3Si3O12(OH)
  • Allanite: (Ca,Ce,La,Y)2(Mn,Fe,Al)3Si3O12(OH)
  • Mukhinite: Ca2(Al2V)Si3O12(OH)
  • Hancockite: (Pb,Ca,Sr)2(Al,Fe) 3Si3O12(OH)
Pleochroism 
  • None in clinozoisite.
  • Distinct red to yellowish brown in hancockite.
  • Allanite: reddish brown/brownish yellow/greenish brown; light brown/brown/dark red-brown; colorless/pale green/green.
  • Epidote: colorless, pale yellow or yellow-green/greenish yellow/yellow-green.
  • Piedmontite: yellow/amethystine violet/red.
Optics See “Identifying Characteristics” below.
EtymologyEpidote is derived from the Greek for “increase,” since the base of the prism has one side longer than the other. Clinozoisite is the monoclinic dimorph of zoisite. Piedmontite (or piemontite) is named after the locality in Italy, Piemonte (Piedmont). Unakite is named after the Unaka range of mountains in the United States. Allanite is named after mineralogist T. Allan. Tawmawite is named after the Myanmar locality. Mukhinite is named after A. S. Mukhin, Soviet geologist.
OccurrenceThe minerals of the epidote group form at low temperatures in low to medium-grade metamorphic rocks. Allanite is more commonly found in igneous rocks such as pegmatites. Clinozoisite and epidote are also found in igneous rocks, and piedmontite is found in schists and manganese ore deposits.
Inclusions Fibrous inclusions, needles, growth zoning.
faceted epidote - Mexico and Kenya
Epidote: Baja California, Mexico (1.0), Kenya (1.2). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Comments

Although epidotes have loaned their name to the epidote mineral supergroup, the gems themselves form a clinozoisite-epidote solid-solution series within this taxon. In 2006, this grouping lost all varieties of zoisite, including its most well-known member, tanzanite. Zoisite is a orthorhombic polymorph of monoclinic clinozoisite. Mineralogists reclassified and removed zoisite from the group, since all other epidote members had monoclinic crystal systems.

Nevertheless, the supergroup still includes some interesting gemstones, both widespread and rare. It features species suitable for faceting and cabbing as well as beautiful crystals for collecting. These materials often contain fibrous inclusions. On rare occasions, they create a chatoyant “cat’s eye” effect in cabbed epidotes and clinozoisites.

Epidote

Usually so dark in color, large faceted epidotes result in nearly black, lifeless gems. However, small stones, under 3 to 4 carats, can often turn out as bright and lively faceted gems.

Pistazite or pistacite is a trade name for yellowish green “pistachio-colored” epidote.

Clinozoisite

These gems would actually make better-looking faceted pieces than epidotes. Although clinozoisites aren’t rare, they occur rarely in sizes over 5 carats. The best known source of gem material is Baja California, Mexico. Other localities occasionally yield fine gems. Clinozoisite rarely occurs in pure form. It usually contains some iron, like its series brother, epidote. Clinozoisite shares a chemical formula and outward appearance (but not a crystal system) with zoisite.

clinozoisite - Mexico, epidote supergroup
Clinozoisite: Mexico (1.18). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Allanite

Very dark in color and seldom cut, allanite contains rare-earth and radioactive elements. As a result, these gems become metamict. In other words, they have severe damage to their internal crystalline structure.

Hancockite

This New Jersey gemstone is very rare. Faceted pieces, if any exist, would weigh under 1 to 2 carats.

Mukhinite

This very rare mineral occurs in small grains. First discovered in Gornaya Shoriya, Russia, no cut specimens exist.

Piedmontite

Also known as piemontite, this species is sometimes confused with thulite, a pink manganiferous variety of zoisite. While thulite sometimes appears bright pink, piedmontite typically has a dark brown or reddish color. Thulite can occur in large pieces, but piedmontite seldom occurs in large masses. However, both materials can make lovely cabochons.

piedmontite - Pennsylvania, epidote supergroup
Piedmontite: Adams County, Pennsylvania (~4 inches across). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Tawmawite

A very rare, deep emerald-green colored variety of epidote from Myanmar, this material gets its color from chromium.

Unakite

A popular material for cabochons, unakite, an altered granite, contains green epidote, white to gray quartz, and pink feldspar (orthoclase). The United States produces and exports this widely used lapidary rock, but Ireland, Zimbabwe, and other countries also produce similar material.

unakite stone - epidote supergroup
“Unakite,” tumble polished stone, by Ra’ike. Licensed under CC By 3.0.

Other Lapidary Materials

The light, striped lines of “Zebra Stone” from Arizona may contain epidote.

“Rosalinda,” an ornamental rock from Peru, consists of calcite, scapolite, and red epidote-piedmontite.

Another ornamental rock used for carving, “Bowesite,” from Australia, consists of epidote, diopside, grossular garnet, actinolite, and other gem materials.

“Lapis Nevada” consists of pink thulite, yellow-green epidote, green diopside, and white to lavender scapolite.

Identifying Characteristics

Optics and Specific Gravity

  Clinozoisite Epidote Piedmontite Hancockite Allanite
Specific Gravity 3.21-3.38 3.38-3.49 3.45-3.52 4.03 3.4-4.2
Optics          
a 1.670-1.715 1.715-1.751 1.732-1.794 1.788 1.640-1.791
β 1.675-1.725 1.725-1.784 1.750-1.807 1.81 1.650-1.815
γ 1.690-1.734 1.734-1.797 1.762-1.829 1.83 1.660-1.828
2V (+) 14-90° (-) 90-116° (+) 2-9° (-) 50° (+/-) 40-123°
Birefringence 0.005-0.015 0.015-0.049 0.025-0.073 0.042 0.013-0.036

Sri Lanka produces a yellow-brown epidote with the following properties:

Minas Gerais, Brazil produces cuttable, yellowish-green trichroic crystals. They’re low in iron and have the following properties:

  • Specific Gravity: 3.30 – 3.50
  • Optics: a = 1.722; β = 1.737; y = 1.743.
  • Birefringence: 0.021.

Streak

Epidote may have a gray streak. Please note that streak testing may harm or destroy your specimen. Conduct it on a piece of rough, never a finished gem, only as a last resort.

Synthetics

Scientists have synthesized epidotes for petrological research. Clinozoisite has also been created for mineralogical research. However, there is no known jewelry use for these materials.

Enhancements

Epidotes don’t typically receive any treatments or enhancements.

Sources

Epidote

Untersulzbachthal, Austria is the main source of faceting rough.

Other important gem-quality sources include:

  • Bourg d’Oisans, France: fine crystals.
  • Italy: Piedmont, other localities.
  • Switzerland: many localities.
  • United States: McFall Mine, Ramona, California; Colorado; Connecticut; Idaho; Massachusetts; Michigan; New Hampshire.
  • Australia; Brazil; Czech Republic; Japan; Kenya; Madagascar; Baja California, Mexico; Arendal, Norway; Pakistan; Russia; Slovakia; South Korea; Sri Lanka.
  • Tawmaw, Myanmar: a chrome-rich material, fine deep green color (tawmawite).
  • Outokumpu, Finland: chromiferous epidote (tawmawite).
epidote - Austria
“Epidote,” 5.0 x 1.7 x 0.55 cm, Knappenwand, Untersulzbach valley, Salzburg, Austria. © Rob Lavinsky, www.iRocks.com. Used with permission.

Clinozoisite

Gavilanes, Baja California, Mexico produces brownish facetable crystals.

Other notable gem-quality sources include:

  • Kenya: gray-green crystals.
  • Austria: Goslerwand, Tyrol (type locality).
  • United States: Nevada; Colorado.
  • Timmons, Ontario, Canada; Czech Republic; Iceland; India; Ireland; Italy; Slovakia; Switzerland.

Allanite

Various localities throughout the United States produce this material.

Other sources include:

  • Brazil; Canada; Greenland; Madagascar; Norway; Russia; Sweden.

Hancockite

Franklin, New Jersey, the only notable locality, produces small crystals.

Piedmontite

Piedmontite occurs in sericite schists in Piemonte, Italy. Egypt produces a porphyry colored red by piedmontite. California and Arizona also have many producing localities.

Other sources include:

  • United States: Missouri; Pennsylvania.
  • Morbihan, France; Japan; Otago, New Zealand; Scotland; Vermland, Sweden.

Unakite

Blue Ridge, Unaka Range, North Carolina produces this lapidary material. Other sources include Virginia and Georgia. In addition, Zimbabwe yields a similar rock.

Stone Sizes

Unakite occurs in huge blocks weighing many pounds. Gem cutters often cut it into spheres as well as cabs. Facetable epidote is rare over 5 carat sizes. Cut clinozoisite tends to be even smaller. Allanite is rarely ever cut, except as cabochons. Piedmontite is opaque and massive. It’s also cut only as cabochons.

  • Smithsonian Institution (Washington, DC): 3.9 (epidote, brown, Austria).
  • Devonian Group (Calgary, Alberta, Canada): 7.30 (clinozoisite, brownish, Iran); 6.90 (epidote, brown).
  • Private Collection: 15 (clinozoisite, light brown-green, Baja).
allanite - Brazil, epidote supergroup
A rare example of a faceted allanite. “Allanite,” 11.9 x 5.8 mm, 3.47 carats, elongated rectangle cut, Brazil. © Rob Lavinsky, www.iRocks.com. Used with permission.

Care

Some epidotes may have a hardness of 7, on par with quartz. However, most gem materials in this supergroup have a hardness of 6 or softer. Since these gems also have perfect cleavage and sensitivities to heat and acids, clean them only with a soft brush, mild detergent, and warm water. For jewelry use, have these stones set in protective settings and/or reserve them for occasional wear. For more recommendations, consult our gemstone jewelry care guide.

epidote rough and cut gem - Pakistan
“Epidote (Rough and Cut Set),” 2.1 x 1.6 x 0.8 cm (Crystal), 4.35 ct (Gem), Tormiq, Gilgit-Baltistan (Northern Areas), Pakistan. © Rob Lavinsky, www.iRocks.com. Used with permission.