Epidote: Difference between revisions
Adding local short description: "Sorosilicate mineral", overriding Wikidata description "epidote supergroup, sorosilicate mineral" (Shortdesc helper) |
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{{Short description|Sorosilicate mineral}} |
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{{Update-EB|date=November 2019}} |
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{{Infobox mineral |
{{Infobox mineral |
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| name = Epidote |
| name = Epidote |
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| category = [[Silicate mineral|Sorosilicates]] |
| category = [[Silicate mineral|Sorosilicates]] |
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| boxwidth = |
| boxwidth = |
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| boxbgcolor = |
| boxbgcolor = #79941d |
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| boxtextcolor = white |
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| image = Epidote-119736.jpg |
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| image = Эпидот(пушкинит).jpg |
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| imagesize = |
| imagesize = 290px |
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| caption = Epidote crystals – Deposit topotype |
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| caption = |
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| formula = {Ca<sub>2</sub>}{Al<sub>2</sub>Fe<sup>3+</sup>} |
| formula = {Ca<sub>2</sub>}{Al<sub>2</sub>Fe<sup>3+</sup>}(SiO<sub>4</sub>)(Si<sub>2</sub>O<sub>7</sub>)O(OH) |
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| IMAsymbol = Ep<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> |
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| molweight = |
| molweight = |
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| system = [[Monoclinic]] |
| system = [[monoclinic crystal system|Monoclinic]] |
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| class = Prismatic ( |
| class = Prismatic (2/m) <br/><small>(same [[Hermann–Mauguin notation|H–M symbol]])</small> |
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| symmetry = ''P''2<sub>1</sub>/m |
| symmetry = ''P''2<sub>1</sub>/m |
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| color = Pistachio |
| color = [[shades of chartreuse|Pistachio green]], [[chartreuse (color)|yellow-green]], greenish black, brownish-green, green, black |
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| habit = Prismatic with striations, fibrous, massive |
| habit = Prismatic with [[striation (geology)|striations]], fibrous, massive |
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| twinning = On [100] |
| twinning = On [100] |
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| cleavage = {001} perfect and {100} imperfect |
| cleavage = {001} perfect and {100} imperfect |
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| pleochroism = Strong |
| pleochroism = Strong |
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| streak = Greyish white |
| streak = Greyish white |
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| gravity = 3. |
| gravity = 3.38–3.49 |
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| density = |
| density = |
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| melt = |
| melt = |
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| references = <ref>[http://rruff.geo.arizona.edu/doclib/hom/epidote.pdf Epidote]. ''Handbook of Mineralogy''</ref><ref>[http://www.mindat.org/min-1389.html Epidote]. Mindat</ref><ref>[http://webmineral.com/data/Epidote.shtml Epidote]. Webmineral</ref> |
| references = <ref>[http://rruff.geo.arizona.edu/doclib/hom/epidote.pdf Epidote]. ''Handbook of Mineralogy''</ref><ref>[http://www.mindat.org/min-1389.html Epidote]. Mindat</ref><ref>[http://webmineral.com/data/Epidote.shtml Epidote]. Webmineral</ref> |
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'''Epidote''' is a [[calcium]] [[aluminium]] [[iron]] [[Silicate minerals|sorosilicate]] [[mineral]]. |
'''Epidote''' is a [[calcium]] [[aluminium]] [[iron]] [[Silicate minerals|sorosilicate]] [[mineral]]. |
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==Description== |
==Description== |
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Well developed crystals of epidote, Ca<sub>2</sub>Al<sub>2</sub>(Fe<sup>3+</sup>;Al)(SiO<sub>4</sub>)(Si<sub>2</sub>O<sub>7</sub>)O(OH), [[crystal]]lizing in the [[monoclinic]] system, 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. Many of the characters 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. It displays strong [[pleochroism]], the pleochroic colors being usually green, yellow and brown. [[Clinozoisite]] is green, white or pale rose-red group species containing very little iron, thus having the same chemical composition as the [[orthorhombic]] mineral [[zoisite]]. The name, due to [[René Just Haüy|Haüy]], is derived from the Greek word "epidosis" (ἐπίδοσις) which means "addition" in allusion to one side of the ideal prism being longer than the other. |
Well developed crystals of epidote, Ca<sub>2</sub>Al<sub>2</sub>(Fe<sup>3+</sup>;Al)(SiO<sub>4</sub>)(Si<sub>2</sub>O<sub>7</sub>)O(OH), [[crystal]]lizing in the [[monoclinic]] system, are of frequent occurrence: they are commonly prismatic in habit, the direction of elongation being perpendicular to the single plane of symmetry. The name Epidote is derived from the Greek word 'epidosis', meaning "increase", in allusion to the crystal characteristic of one longer side at the base of the prism.<ref>{{Cite web |title=About Epidote |url=https://www.mindat.org/min-1389.html}}</ref> The faces are often deeply striated and crystals are often twinned. Many of the characters 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. It displays strong [[pleochroism]], the pleochroic colors being usually green, yellow and brown. [[Clinozoisite]] is green, white or pale rose-red group species containing very little iron, thus having the same chemical composition as the [[orthorhombic]] mineral [[zoisite]].<ref name="EB1911">{{EB1911|inline=y|wstitle=Epidote|volume=9|page=689|first=Leonard James|last=Spencer|author-link=Leonard James Spencer}}</ref> The name, due to [[René Just Haüy|Haüy]], is derived from the Greek word "epidosis" (ἐπίδοσις) which means "addition" in allusion to one side of the ideal prism being longer than the other. |
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| ⚫ | Epidote is an abundant rock-forming mineral, but one of secondary origin. It occurs in [[marble]] and [[schist]]ose rocks of [[metamorphic rock|metamorphic]] origin. It is also a product of [[hydrothermal alteration]] of various minerals ([[feldspar]]s, [[mica]]s, [[pyroxene]]s, [[amphibole]]s, [[garnet]]s, and others) composing [[igneous rocks]]. A rock composed of [[quartz]] and epidote is known as [[epidosite]]. Well-developed crystals are found at many localities: Knappenwand, near the [[Großvenediger]] in the Untersulzbachthal in [[Salzburg]], as magnificent, dark green crystals of long prismatic habit in cavities in epidote schist, with [[asbestos]], [[adularia]], [[calcite]], and [[apatite]]; the Ala valley and [[Traversella]] in [[Piedmont]]; Arendal in [[Norway]]; [[Le Bourg-d'Oisans]] in [[Dauphiné]]; [[Haddam, Connecticut|Haddam]] in [[Connecticut]]; [[Prince of Wales Island (Alaska)|Prince of Wales Island]] in [[Alaska]], here as large, dark green, tabular crystals with [[copper]] [[ore]]s in metamorphosed limestone.<ref name="EB1911"/> |
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| ⚫ | |||
| ⚫ | |||
| ⚫ | Epidote is an abundant rock-forming mineral, but one of secondary origin. It occurs in [[marble]] and [[schist]]ose rocks of [[metamorphic rock|metamorphic]] origin. It is also a product of [[hydrothermal alteration]] of various minerals ([[feldspar]]s, [[mica]]s, [[pyroxene]]s, [[amphibole]]s, [[garnet]]s, and others) composing [[igneous rocks]]. A rock composed of [[quartz]] and epidote is known as [[epidosite]]. Well-developed crystals are found at many localities: Knappenwand, near the [[Großvenediger]] in the Untersulzbachthal in [[Salzburg]], as magnificent, dark green crystals of long prismatic habit in cavities in epidote schist, with [[asbestos]], [[adularia]], [[calcite]], and [[apatite]]; the Ala valley and [[Traversella]] in [[Piedmont]]; Arendal in [[Norway]]; [[Le Bourg-d'Oisans]] in [[Dauphiné]]; [[Haddam, Connecticut|Haddam]] in [[Connecticut]]; [[Prince of Wales Island (Alaska)|Prince of Wales Island]] in [[Alaska]], here as large, dark green, tabular crystals with [[copper]] [[ore]]s in metamorphosed limestone. |
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| ⚫ | |||
===Related species=== |
===Related species=== |
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Belonging to the same isomorphous group with epidote are the [[Rare-earth element|REE-rich]] [[allanite]] (containing primarily [[lanthanum]], [[cerium]], and [[yttrium]]), and the [[manganese]]-rich [[piemontite]]. |
Belonging to the same isomorphous group with epidote are the [[Rare-earth element|REE-rich]] [[allanite]] (containing primarily [[lanthanum]], [[cerium]], and [[yttrium]]), and the [[manganese]]-rich [[piemontite]]. |
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Piemontite occurs as small, reddish-black, monoclinic crystals in the manganese mines at San Marcel, near [[Ivrea]] in Piedmont, and in crystalline schists at several places in [[Japan]]. The purple color of the [[Egypt]]ian porfido rosso antico is due to the presence of this mineral. |
Piemontite occurs as small, reddish-black, monoclinic crystals in the manganese mines at San Marcel, near [[Ivrea]] in Piedmont, and in crystalline schists at several places in [[Japan]]. The purple color of the [[Egypt]]ian porfido rosso antico is due to the presence of this mineral.<ref name="EB1911"/> |
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| ⚫ | Allanite and [[dollaseite-(Ce)]] have the same general epidote formula and contain metals of the cerium group. In external appearance allanite differs widely from epidote, being black or dark brown in color, pitchy in lustre, and opaque in the mass; further, there is little or no cleavage, and well-developed crystals are rare. The crystallographic and optical characters are similar to those of epidote; the pleochroism is strong with reddish-, yellowish-, and greenish-brown colors. Although not a common mineral, allanite is of fairly wide distribution as a primary accessory constituent of many crystalline rocks, [[gneiss]], [[granite]], [[syenite]], [[rhyolite]], [[andesite]], and others. It was first found in the granite of east [[Greenland]] and described by [[Thomas Allan (mineralogist)|Thomas Allan]] in 1808, after whom the species was named. Allanite is a mineral readily altered by hydration, becoming optically isotropic and [[amorphous]]: for this reason several varieties have been distinguished, and many different names applied. Orthite was the name given by [[Jöns Berzelius]] in 1818 to a hydrated form found as slender prismatic crystals, sometimes a foot in length, at Finbo, near [[Falun]] in [[Sweden]].<ref name="EB1911"/> Dollaseite is less common, famous from the Ostanmossa mine in the [[Norberg]] district of [[Sweden]]. |
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[[Image:Dollaseite.JPG|thumb|left|Sample of dollaseite (dark brown matrix at arrow points) from Sweden]] |
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| ⚫ | Allanite and [[dollaseite-(Ce)]] have the same general epidote formula and contain metals of the cerium group. In external appearance allanite differs widely from epidote, being black or dark brown in color, pitchy in lustre, and opaque in the mass; further, there is little or no cleavage, and well-developed crystals are rare. The crystallographic and optical characters are similar to those of epidote; the pleochroism is strong with reddish-, yellowish-, and greenish-brown colors. Although not a common mineral, allanite is of fairly wide distribution as a primary accessory constituent of many crystalline rocks, [[gneiss]], [[granite]], [[syenite]], [[rhyolite]], [[andesite]], and others. It was first found in the granite of east [[Greenland]] and described by [[Thomas Allan]] in 1808, after whom the species was named. Allanite is a mineral readily altered by hydration, becoming optically isotropic and [[amorphous]]: for this reason several varieties have been distinguished, and many different names applied. Orthite was the name given by [[Jöns Berzelius]] in 1818 to a hydrated form found as slender prismatic crystals, sometimes a foot in length, at Finbo, near [[Falun]] in [[Sweden]]. Dollaseite is less common, famous from the Ostanmossa mine in the [[Norberg]] district of [[Sweden]]. |
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==Gallery== |
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<gallery mode=packed> |
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Epidotic vesicular basalt (Portage Lake Volcanic Series, upper Mesoproterozoic, 1.093 to 1.097 Ga; Gratiot Mine, Keweenaw Peninsula, Upper Peninsula of Michigan, USA) 3 (9393657643).jpg|Vesicular [[basalt]] with epidote crystal filling |
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Deformed epidote lens in amphibole epidote schist.jpg|Deformed epidote within [[greenschist]] rock from [[Itogon]], Philippines |
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Amygdaloidal basalt (Portage Lake Volcanic Series, upper Mesoproterozoic, 1.093 to 1.097 Ga; Keweenaw Peninsula, Upper Peninsula of Michigan, USA) 13.jpg|Amygdaloidal basalt filled with epidote |
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Epidote-lined vug in basalt (Portage Lake Volcanic Series, upper Mesoproterozoic, 1.093 to 1.097 Ga; Centennial Mine, Keweenaw Peninsula, Upper Peninsula of Michigan, USA) 2.jpg|[[Vug]] in basalt lined with epidote |
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ÉpidoteFrance Ref374 MuséumHistoireNaturelleLille GLAM2016 Photo.F.Lamiot 19.jpg|Epidote from [[France]] |
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Epidot - Haidarabad, Dolina Shigar, Skardu, Pakistan.jpg|Epidote from [[Pakistan]] |
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Epidote - Canta, Lima, Peru.jpg|Epidote from [[Lima]], [[Peru]] |
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Epidot DSC 5229.jpg|Epidote from [[Germany]] |
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ÉpidoteFrance Ref374 MuséumHistoireNaturelleLille GLAM2016 Photo.F.Lamiot 5.jpg|Epidote from France |
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</gallery> |
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==References== |
==References== |
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{{Reflist}} |
{{Reflist}} |
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*{{EB1911 |wstitle=Epidote |volume=9 |page=689 |first=Leonard James |last=Spencer}} |
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==External links== |
==External links== |
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{{Commons category|Epidote}} |
{{Commons category|Epidote}} |
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* [https://web.archive.org/web/20040603093346/http://mineral.galleries.com/minerals/silicate/epidote/epidote.htm The mineral Epidote Mineral Galleries] |
* [https://web.archive.org/web/20040603093346/http://mineral.galleries.com/minerals/silicate/epidote/epidote.htm The mineral Epidote Mineral Galleries] |
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{{Authority control}} |
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[[Category:Calcium minerals]] |
[[Category:Calcium minerals]] |
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[[Category:Epidote group]] |
[[Category:Epidote group]] |
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[[Category:Monoclinic minerals]] |
[[Category:Monoclinic minerals]] |
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[[Category:Minerals in space group 11]] |
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Latest revision as of 04:45, 30 June 2024
 | This article is largely based on an article in the out-of-copyright Encyclopædia Britannica Eleventh Edition, which was produced in 1911. (November 2019) |
| Epidote | |
|---|---|
.jpg) | |
| General | |
| Category | Sorosilicates |
| Formula (repeating unit) | {Ca2}{Al2Fe3+}(SiO4)(Si2O7)O(OH) |
| IMA symbol | Ep[1] |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H–M symbol) |
| Space group | P21/m |
| Identification | |
| Color | Pistachio green, yellow-green, greenish black, brownish-green, green, black |
| Crystal habit | Prismatic with striations, fibrous, massive |
| Twinning | On [100] |
| Cleavage | {001} perfect and {100} imperfect |
| Fracture | Flat regular to uneven |
| Mohs scale hardness | 6–7 |
| Luster | Vitreous to resinous |
| Streak | Greyish white |
| Diaphaneity | Transparent to nearly opaque |
| Specific gravity | 3.38–3.49 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.715–1.751 nβ = 1.725–1.784 nγ = 1.734–1.797 |
| Birefringence | δ = 0.019–0.046 |
| Pleochroism | Strong |
| References | [2][3][4] |
Epidote is a calcium aluminium iron sorosilicate mineral.
Description
[edit]Well developed crystals of epidote, Ca2Al2(Fe3+;Al)(SiO4)(Si2O7)O(OH), crystallizing in the monoclinic system, are of frequent occurrence: they are commonly prismatic in habit, the direction of elongation being perpendicular to the single plane of symmetry. The name Epidote is derived from the Greek word 'epidosis', meaning "increase", in allusion to the crystal characteristic of one longer side at the base of the prism.[5] The faces are often deeply striated and crystals are often twinned. Many of the characters 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. It displays strong pleochroism, the pleochroic colors being usually green, yellow and brown. Clinozoisite is green, white or pale rose-red group species containing very little iron, thus having the same chemical composition as the orthorhombic mineral zoisite.[6] The name, due to Haüy, is derived from the Greek word "epidosis" (ἐπίδοσις) which means "addition" in allusion to one side of the ideal prism being longer than the other.
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. Well-developed crystals are found at many localities: Knappenwand, near the Großvenediger in the Untersulzbachthal in Salzburg, as magnificent, dark green crystals of long prismatic habit in cavities in epidote schist, with asbestos, adularia, calcite, and apatite; the Ala valley and Traversella in Piedmont; Arendal in Norway; Le Bourg-d'Oisans in Dauphiné; Haddam in Connecticut; Prince of Wales Island in Alaska, here as large, dark green, tabular crystals with copper ores in metamorphosed limestone.[6]
The perfectly transparent, dark green crystals from the Knappenwand and from Brazil have occasionally been cut as gemstones.[6] The green part of several mixed-rock ornamental stones is composed of epidote. These include Unakite and Australian Dragon Bloodstone.
Related species
[edit]Belonging to the same isomorphous group with epidote are the REE-rich allanite (containing primarily lanthanum, cerium, and yttrium), and the manganese-rich piemontite.
Piemontite occurs as small, reddish-black, monoclinic crystals in the manganese mines at San Marcel, near Ivrea in Piedmont, and in crystalline schists at several places in Japan. The purple color of the Egyptian porfido rosso antico is due to the presence of this mineral.[6]
Allanite and dollaseite-(Ce) have the same general epidote formula and contain metals of the cerium group. In external appearance allanite differs widely from epidote, being black or dark brown in color, pitchy in lustre, and opaque in the mass; further, there is little or no cleavage, and well-developed crystals are rare. The crystallographic and optical characters are similar to those of epidote; the pleochroism is strong with reddish-, yellowish-, and greenish-brown colors. Although not a common mineral, allanite is of fairly wide distribution as a primary accessory constituent of many crystalline rocks, gneiss, granite, syenite, rhyolite, andesite, and others. It was first found in the granite of east Greenland and described by Thomas Allan in 1808, after whom the species was named. Allanite is a mineral readily altered by hydration, becoming optically isotropic and amorphous: for this reason several varieties have been distinguished, and many different names applied. Orthite was the name given by Jöns Berzelius in 1818 to a hydrated form found as slender prismatic crystals, sometimes a foot in length, at Finbo, near Falun in Sweden.[6] Dollaseite is less common, famous from the Ostanmossa mine in the Norberg district of Sweden.
Gallery
[edit]-
Vesicular basalt with epidote crystal filling -
Deformed epidote within greenschist rock from Itogon, Philippines -
Amygdaloidal basalt filled with epidote -
Vug in basalt lined with epidote -
Epidote from France -
Epidote from Russia -
Epidote from Pakistan -
-
Epidote from Germany -
Epidote from France
_3_(9393657643).jpg)
_13.jpg)
_2.jpg)
References
[edit]- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ Epidote. Handbook of Mineralogy
- ^ Epidote. Mindat
- ^ Epidote. Webmineral
- ^ "About Epidote".
- ^ a b c d e One or more of the preceding sentences incorporates text from a publication now in the public domain: Spencer, Leonard James (1911). "Epidote". In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 9 (11th ed.). Cambridge University Press. p. 689.
External links
[edit]
