Physical, geochemical and gemological properties of opals from Faroe islands
The opals from Faroe Islands are commercially not very relevant but are important from the historical point of view. Nice yellowish-red color fire opal and common opals from these islands are also very appreciated by collectors and can reach high prices in the markets. The analysed opals derive from...
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ftunivpavia:oai:iris.unipv.it:11571/765432 2024-04-14T08:11:20+00:00 Physical, geochemical and gemological properties of opals from Faroe islands CAUCIA, FRANCA PIERA MARINONI, LUIGI TITO Leone A. Caucia, FRANCA PIERA Marinoni, LUIGI TITO Leone, A. 2013 STAMPA http://hdl.handle.net/11571/765432 eng eng info:eu-repo/semantics/altIdentifier/wos/WOS:000326682000002 volume:191 issue:1 firstpage:33 lastpage:43 numberofpages:11 journal:NEUES JAHRBUCH FUR MINERALOGIE-ABHANDLUNGEN http://hdl.handle.net/11571/765432 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84891682307 info:eu-repo/semantics/article 2013 ftunivpavia 2024-03-21T15:52:45Z The opals from Faroe Islands are commercially not very relevant but are important from the historical point of view. Nice yellowish-red color fire opal and common opals from these islands are also very appreciated by collectors and can reach high prices in the markets. The analysed opals derive from Hoyvik near Torsshavn, in the island of Streymoy. Parent rocks are represented by the "middle basalt" formation. Investigated opals generally show vitreous-dull luster and specific gravity values comparable with data in literature. They are generally CT type with variable contents of cristobalite and tridymite and, in some cases, chalcedony. In order of abundance, trace elements are represented by Fe, Al, Ca, Mg, Na, P and K; Fe contents are very variable. The distribution of the elements is dictated expecially by cristallochemical substitution in the pseudo crystalline structure of the opals. A distinct feature of the opals from Faroe is represented by the presence of P; this element probably derives from metasomatic fluids. Trace elements probably derive from feldspars and pyroxenes in the host basaltic rocks. SEM investigations highlighted different textures like random piling of individual nanograins, lepispheres, tablets and plates that are typical of magmatic CT opals. The variable chemical composition and physical properties, and the different microtextures, would indicate the opals from Faroe Islands formed from different solutions, through variable growth rates. Article in Journal/Newspaper Faroe Islands Streymoy IRIS UNIPV (Università degli studi di Pavia) Faroe Islands Streymoy ENVELOPE(-7.000,-7.000,62.133,62.133) |
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Open Polar |
collection |
IRIS UNIPV (Università degli studi di Pavia) |
op_collection_id |
ftunivpavia |
language |
English |
description |
The opals from Faroe Islands are commercially not very relevant but are important from the historical point of view. Nice yellowish-red color fire opal and common opals from these islands are also very appreciated by collectors and can reach high prices in the markets. The analysed opals derive from Hoyvik near Torsshavn, in the island of Streymoy. Parent rocks are represented by the "middle basalt" formation. Investigated opals generally show vitreous-dull luster and specific gravity values comparable with data in literature. They are generally CT type with variable contents of cristobalite and tridymite and, in some cases, chalcedony. In order of abundance, trace elements are represented by Fe, Al, Ca, Mg, Na, P and K; Fe contents are very variable. The distribution of the elements is dictated expecially by cristallochemical substitution in the pseudo crystalline structure of the opals. A distinct feature of the opals from Faroe is represented by the presence of P; this element probably derives from metasomatic fluids. Trace elements probably derive from feldspars and pyroxenes in the host basaltic rocks. SEM investigations highlighted different textures like random piling of individual nanograins, lepispheres, tablets and plates that are typical of magmatic CT opals. The variable chemical composition and physical properties, and the different microtextures, would indicate the opals from Faroe Islands formed from different solutions, through variable growth rates. |
author2 |
Caucia, FRANCA PIERA Marinoni, LUIGI TITO Leone, A. |
format |
Article in Journal/Newspaper |
author |
CAUCIA, FRANCA PIERA MARINONI, LUIGI TITO Leone A. |
spellingShingle |
CAUCIA, FRANCA PIERA MARINONI, LUIGI TITO Leone A. Physical, geochemical and gemological properties of opals from Faroe islands |
author_facet |
CAUCIA, FRANCA PIERA MARINONI, LUIGI TITO Leone A. |
author_sort |
CAUCIA, FRANCA PIERA |
title |
Physical, geochemical and gemological properties of opals from Faroe islands |
title_short |
Physical, geochemical and gemological properties of opals from Faroe islands |
title_full |
Physical, geochemical and gemological properties of opals from Faroe islands |
title_fullStr |
Physical, geochemical and gemological properties of opals from Faroe islands |
title_full_unstemmed |
Physical, geochemical and gemological properties of opals from Faroe islands |
title_sort |
physical, geochemical and gemological properties of opals from faroe islands |
publishDate |
2013 |
url |
http://hdl.handle.net/11571/765432 |
long_lat |
ENVELOPE(-7.000,-7.000,62.133,62.133) |
geographic |
Faroe Islands Streymoy |
geographic_facet |
Faroe Islands Streymoy |
genre |
Faroe Islands Streymoy |
genre_facet |
Faroe Islands Streymoy |
op_relation |
info:eu-repo/semantics/altIdentifier/wos/WOS:000326682000002 volume:191 issue:1 firstpage:33 lastpage:43 numberofpages:11 journal:NEUES JAHRBUCH FUR MINERALOGIE-ABHANDLUNGEN http://hdl.handle.net/11571/765432 info:eu-repo/semantics/altIdentifier/scopus/2-s2.0-84891682307 |
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1796309035340791808 |