Portlandite: Difference between revisions
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{{Short description|Calcium hydroxide mineral}} |
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{{Infobox mineral |
{{Infobox mineral |
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| name = Portlandite |
| name = Portlandite |
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| caption = Portlandite and [[ettringite]] |
| caption = Portlandite and [[ettringite]] |
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| formula = Ca(OH)<sub>2</sub> |
| formula = Ca(OH)<sub>2</sub> |
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| IMAsymbol = Por<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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| class = Hexagonal scalenohedral ({{overline|3}}m) <br/>[[H-M symbol]]: ({{overline|3}} 2/m) |
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| color = Colorless, white to greenish white |
| color = Colorless, white to greenish white |
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| colour = |
| colour = |
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| habit = Hexagonal plates; commonly fibrous, powdery, massive. |
| habit = Hexagonal plates; commonly fibrous, powdery, massive. |
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| twinning = |
| twinning = |
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| cleavage = Perfect on {0001} |
| cleavage = Perfect on {0001} |
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| density = |
| density = |
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| polish = |
| polish = |
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| opticalprop = Uniaxial ( |
| opticalprop = Uniaxial (−) |
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| refractive = n<sub>ω</sub> = 1.574 n<sub>ε</sub> = 1.547 |
| refractive = n<sub>ω</sub> = 1.574 n<sub>ε</sub> = 1.547 |
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| birefringence = δ = 0.027 |
| birefringence = δ = 0.027 |
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| other = |
| other = |
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| alteration = Alters to CaCO<sub>3</sub> on exposure to CO<sub>2</sub> bearing waters |
| alteration = Alters to CaCO<sub>3</sub> on exposure to CO<sub>2</sub> bearing waters |
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| references = <ref name=Handbook> |
| references = <ref>{{Cite web|url=https://www.mineralienatlas.de/lexikon/index.php/MineralData?lang=de&mineral=Portlandite|title=Mineralienatlas - Fossilienatlas|website=www.mineralienatlas.de}}</ref><ref name=Handbook>{{Cite web|url=http://rruff.geo.arizona.edu/doclib/hom/portlandite.pdf|title=Handbook of Mineralogy}}</ref><ref name=Mindat>{{Cite web|url=https://www.mindat.org/min-3264.html|title=Portlandite: Mineral information, data and localities.|website=www.mindat.org}}</ref><ref name=Webmin>{{Cite web|url=http://www.webmineral.com/data/Portlandite.shtml|title=Portlandite Mineral Data|website=www.webmineral.com}}</ref><ref>{{cite book |first1=Charles |last1=Pallache |authorlink=Charles Palache |first2=Harry |last2=Berman |first3=Clifford |last3=Frondel |title=The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana |publisher=Wiley |year=1944 |isbn=9780471192398 |edition=7 |pages=641–642 }}</ref> |
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(7th edition), v. I, pp. 641–642</ref> |
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'''Portlandite''' is a |
'''Portlandite''' is a [[hydroxide]]-bearing mineral typically included in the [[oxide mineral]] class. It is the naturally occurring form of [[calcium hydroxide]] (Ca(OH)<sub>2</sub>) and the calcium analogue of [[brucite]] (Mg(OH)<sub>2</sub>). |
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==Occurrence== |
==Occurrence== |
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Portlandite occurs in a variety of environments. At the [[Type locality (geology)|type location]] in Northern Ireland it occurs as an alteration of [[calc–silicate rock]]s by [[contact metamorphism]] of [[larnite]]–[[spurrite]]. It occurs as [[fumarole]] deposits in the [[Vesuvius]] area. In Jebel Awq, [[Oman]] it occurs as precipitates from an [[alkaline]] [[Spring (hydrology)|spring]] emanating from [[ultramafic]] bedrock. In the [[Chelyabinsk]] coal basin of [[Russia]] it is produced by combustion of [[coal]] seams and similarly by spontaneous combustion of [[bitumen]] in the Hatrurim Formation of the [[Negev desert]] in [[Israel]] and the Maqarin area, [[Jordan]].<ref name=Handbook/> It also occurs in the [[manganese]] mining area of [[Kuruman]], [[Cape Province]], [[South Africa]] in the [[Kalahari Desert]] where it occurs as large crystals and masses.<ref name=Mindat/><ref name=Handbook/> |
Portlandite occurs in a variety of environments. At the [[Type locality (geology)|type location]] in Northern Ireland it occurs as an alteration of [[calc–silicate rock]]s by [[contact metamorphism]] of [[larnite]]–[[spurrite]]. It occurs as [[fumarole]] deposits in the [[Vesuvius]] area. In Jebel Awq, [[Oman]], it occurs as precipitates from an [[alkaline]] [[Spring (hydrology)|spring]] emanating from [[ultramafic]] bedrock. In the [[Chelyabinsk]] coal basin of [[Russia]] it is produced by combustion of [[coal]] seams and similarly by spontaneous combustion of [[bitumen]] in the Hatrurim Formation of the [[Negev desert]] in [[Israel]] and the Maqarin area, [[Jordan]].<ref name=Handbook/> It also occurs in the [[manganese]] mining area of [[Kuruman]], [[Cape Province]], [[South Africa]] in the [[Kalahari Desert]] where it occurs as large crystals and masses.<ref name=Mindat/><ref name=Handbook/> |
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It occurs in association with [[afwillite]], [[calcite]], [[larnite]], [[spurrite]], [[halite]], [[brownmillerite]], [[hydrocalumite]], [[mayenite]] and [[ettringite]].<ref name=Handbook/> |
It occurs in association with [[afwillite]], [[calcite]], [[larnite]], [[spurrite]], [[halite]], [[brownmillerite]], [[hydrocalumite]], [[mayenite]] and [[ettringite]].<ref name=Handbook/> |
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[[Category:Hydroxide minerals]] |
[[Category:Hydroxide minerals]] |
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[[Category:Trigonal minerals]] |
[[Category:Trigonal minerals]] |
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[[Category:Minerals in space group 164]] |
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Latest revision as of 14:23, 16 March 2024
| Portlandite | |
|---|---|
 Portlandite and ettringite | |
| Allgemein | |
| Kategorie | Oxide mineral |
| Formula (repeating unit) | Ca(OH)2 |
| IMA symbol | Por[1] |
| Strunz classification | 4.FE.05 |
| Dana classification | 06.02.01.04 Brucite group |
| Crystal system | Trigonal |
| Crystal class | Hexagonal scalenohedral (3m) H-M symbol: (3 2/m) |
| Space group | P3m1 |
| Unit cell | a = 3.589 Å, c = 4.911 Å; Z = 1 |
| Identification | |
| Color | Colorless, white to greenish white |
| Crystal habit | Hexagonal plates; commonly fibrous, powdery, massive. |
| Cleavage | Perfect on {0001} |
| Tenacity | Sectile with flexible cleavage plates |
| Mohs scale hardness | 2 |
| Luster | Pearly on cleavages |
| Diaphaneity | Transparent |
| Specific gravity | 2.23 |
| Optical properties | Uniaxial (−) |
| Refractive index | nω = 1.574 nε = 1.547 |
| Birefringence | δ = 0.027 |
| Solubility | Soluble in water producing an alkaline solution |
| Alters to | Alters to CaCO3 on exposure to CO2 bearing waters |
| References | [2][3][4][5][6] |
Portlandite is a hydroxide-bearing mineral typically included in the oxide mineral class. It is the naturally occurring form of calcium hydroxide (Ca(OH)2) and the calcium analogue of brucite (Mg(OH)2).
Occurrence
[edit]Portlandite occurs in a variety of environments. At the type location in Northern Ireland it occurs as an alteration of calc–silicate rocks by contact metamorphism of larnite–spurrite. It occurs as fumarole deposits in the Vesuvius area. In Jebel Awq, Oman, it occurs as precipitates from an alkaline spring emanating from ultramafic bedrock. In the Chelyabinsk coal basin of Russia it is produced by combustion of coal seams and similarly by spontaneous combustion of bitumen in the Hatrurim Formation of the Negev desert in Israel and the Maqarin area, Jordan.[3] It also occurs in the manganese mining area of Kuruman, Cape Province, South Africa in the Kalahari Desert where it occurs as large crystals and masses.[4][3]
It occurs in association with afwillite, calcite, larnite, spurrite, halite, brownmillerite, hydrocalumite, mayenite and ettringite.[3]
It was first described in 1933 for an occurrence at Scawt Hill, Larne, County Antrim, Northern Ireland. It was named portlandite because the chemical calcium hydroxide is a common hydrolysis product of Portland cement.[4][3]
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.
- ^ "Mineralienatlas - Fossilienatlas". www.mineralienatlas.de.
- ^ a b c d e "Handbook of Mineralogy" (PDF).
- ^ a b c "Portlandite: Mineral information, data and localities". www.mindat.org.
- ^ "Portlandite Mineral Data". www.webmineral.com.
- ^ Pallache, Charles; Berman, Harry; Frondel, Clifford (1944). The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana (7 ed.). Wiley. pp. 641–642. ISBN 9780471192398.