Name/Title
EpidoteEntry/Object ID
2009.62.42Description
Chemical Composition: Ca2Al2(Fe3+;Al)(SiO4)(Si2
Crystal System: Monoclinic System
Description: Common Name: Epidote
Chemistry: Ca2(Al, Fe)3(SiO4)3(OH), Calcium Aluminum Iron Silicate Hydroxide.
Group: Silicates
Location: Minas Grais, Brazil
Description: Green and black crystals
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.
Best Field Indicators only one direction of cleavage, crystal habit, color and hardnessls
Fracture: uneven to conchoidal
Hardness: 7 Quartz
Luster: Vitreous
Occurrence: Epidote is an abundant rock-forming mineral, but one 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. A rock composed of quartz and epidote is known as epidosite.
Rock Type: Metamorphic
Specific Gravity: 3.3 - 3.5
Streak: white to gray
Texture: crystaline
Variety: 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 specimensCollection
RAGM Mineral CollectionDimensions
Width
3-1/2 inDepth
3 inLength
4 inWeight
1.224 ozDimension Notes
Dimension taken at widest pointsLocation
Location
Display Case
FS-4Room
Frieda Smith HallBuilding
Crater Rock MuseumCategory
PermanentDate
August 18, 2023