THE MINERAL EPIDOTE

  • Chemistry: Ca2(Al, Fe)3(SiO4)3(OH), Calcium Aluminum Iron Silicate Hydroxide.
  • Class: Silicates
  • Subclass: Sorosilicates
  • Group: Epidote
  • Uses: mineral specimens and rarely as a gemstone.
  • Specimens
Epidote is a structurally complex mineral having both single silicate tetrahedrons, SiO4, and double silicate tetrahedrons, Si2O7. The formula of epidote could be expressed in a such a way so as to reflect this organization; Ca2(Al, Fe)Al2O(SiO4)(Si2O7)(OH). The two aluminums represent the parallel chains of AlO6 and AlO4(OH)2 octahedra that are the heart of the epidote structure. The silicate groups and extra ions connect the chains together. Since the chains are parallel, the crystals tend to be prismatic. The chains are arranged in parallel planes and the perfect cleavage breaks the bonds between these planes. Epidote, while not general known for exceptional crystals can produce some magnificent specimens. Its unique green color which is often described as "pistachio", is quite striking in well colored specimens.

PHYSICAL CHARACTERISTICS:

  • Color is "pistachio" green to yellowish or brownish green, also brown to black.
  • Luster is vitreous.
  • Transparency crystals are transparent to translucent.
  • Crystal System monoclinic; 2/m
  • Crystal Habits include long, somewhat prismatic or tabular crystals with a typically dominant pinacoid that the crystal is often flattened against. The terminations are wedge shaped or tappered pyramids. Many clusters show grooved slender crystals or acicular sprays. Also massive, fiberous or granular.
  • Cleavage good in one direction lengthwise.
  • Fracture is uneven to conchoidal.
  • Hardness is 6-7
  • Specific Gravity is 3.3-3.5
  • Streak white to gray
  • Associated Minerals calcite, biotite, hornblende, actinolite, andradite garnet and other metamorphic minerals.
  • Other Characteristics: striated to the depth of grooves in some crystals.
  • Notable Occurances Untersulzbachtal, Austria; Italy; Baja, Mexico and many localities in the USA.
  • Best Field Indicators only one direction of cleavage, crystal habit, color and hardness.
This Site Awarded
Available EPIDOTE specimens:
EPIDOTE specimen EPI-18
$ 36.00 -10% = $ 32.40
Dims: 1.56x0.97x0.96in (3.96x2.46x2.43cm) .... Wt: 1.41oz (40.0g) .... Loc: Green Monster Mine, Prince of Wales Island, Alaska, USA
This crystal is essentially black, although its green color is evident along fractures and some edges. While showing damage where it was removed from the host rock, and where other minerals were detached, it shows four of the six sides, plus it is doubly-terminated. Half of the faces have a vitreous luster, the others are dull.
no photo
EPI-18
$ 32.40
no photo
EPIDOTE specimen EPI-19
$ 60.00 -10% = $ 54.00
Dims: 1.72x1.44x0.79in (4.37x3.66x2.01cm) .... Wt: 1.10oz (31.0g) .... Loc: Knappenwand, Salzburg, Austria
The epidot crystals of this specimen look black. A loupe (and bright lights) reveals that some of them are actually a transparent green, but most appear brown.
no photo
EPI-19
$ 54.00
no photo
EPIDOTE specimen EPI-22
$ 40.00
Dims: 2.47x1.56x1.26in (6.26x3.96x3.19cm) .... Wt: 4.4oz (124g) .... Loc: Hongxi, Sichuan, China
This is a beautiful and complex multi-mineral specimen. Worse, I'm not sure of the identity of several of the minerals. The bulk of the specimen is epidote, and I think I detect three different forms and/or habits. At first glance the epidote is obvious, the dark grass-green crystals coverering most of the specimen. Under a loupe, however, some of those crystals appear to be a bright-green epidote over black crystals, which I'm certain are more epidote, only transparent and thus appearing black. On the back is a lighter green (the color of peridot) with a radial structure and a silky luster, but it reminds me of one of the finest epidot specimens we've had, but a similar cluster looks like wavelite. There are patches of a teal mineral and an orange mineral (both unidentified), but for an added treat there are several crystals of copper - most unusual, and very nice!
no photo
EPI-22
$ 40.00
no photo
see this List of ALL specimens including SOLD ones
 
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