{"id":2918,"date":"2017-04-28T11:34:25","date_gmt":"2017-04-28T09:34:25","guid":{"rendered":"http:\/\/agora.xtec.cat\/iesm-jmzafra\/?p=2918"},"modified":"2018-06-07T12:29:29","modified_gmt":"2018-06-07T10:29:29","slug":"obsidiana","status":"publish","type":"post","link":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/general\/obsidiana\/","title":{"rendered":"OBSIDIANA"},"content":{"rendered":"

Nom:<\/strong>
\nCatal\u00e0: Obsidiana <\/strong><\/p>\n

Castell\u00e0: Obsidiana<\/p>\n

Angl\u00e8s: Obsidian<\/p>\n

Franc\u00e8s: Obsidienne<\/p>\n

\"Resultado\"Resultado<\/p>\n

 <\/p>\n

Quin tipus i subtipus de roca i\/o mineral \u00e9s?<\/strong><\/p>\n

L\u2019 obsidiana \u00e9s una roca volc\u00e0nica, ja que s\u2019ha produ\u00eft per un refredament r\u00e0pid de la lava. Aquesta, pertany al grup dels Silicats, ja que est\u00e0 formada per diferents minerals.
\nFormaci\u00f3 de la roca i\/o mineral:<\/strong>
\nL’obsidiana es produeix quan un volc\u00e0 emet lava f\u00e9lsica que es refreda r\u00e0pidament amb un creixement m\u00ednim de vidres.<\/p>\n

Composici\u00f3 qu\u00edmica:<\/strong>
\nAquesta roca est\u00e0 formada per silicats d\u2019alumini i un 70% o m\u00e9s de s\u00edlice o di\u00f2xid de silici. El compost qu\u00edmic \u00abdi\u00f2xid de silici\u00bb \u00e9s el principal que constitueix la sorra amb forma de quars. La composici\u00f3 de la sorra varia en els diferents casos de la geologia i les condicions locals. La composici\u00f3 de l\u2019Obsidiana \u00e9s molt semblant a la del granit,
\nest\u00e0 formada per lava fosa, molt poca aigua (aproximadament nom\u00e9s un 2%) i de gasos procedents del volc\u00e0.<\/p>\n

Breu descripci\u00f3 (color, textura…):<\/strong>
\nT\u00e9 la qualitat de canviar el seu color segons la manera de tallar-se. Si es talla paral\u00b7lelament el seu color \u00e9s negre, per\u00f2 tallada perpendicularment el seu color \u00e9s gris.<\/p>\n

Usos i\/o aplicacions<\/strong>
\nAquesta roca s\u2019acostuma a utilitzar com a ornament. Hi ha una cosa molt curiosa sobre el color d\u2019aquesta roca, i \u00e9s que segons la seva forma de tallar-la pot canviar el seu aspecte. Pot passar de ser de color negre a gris.<\/p>\n

Lloc d’origen (Jaciments m\u00e9s importants)<\/strong>
\nLa primera evidencia que hi ha de l\u2019utilitzaci\u00f3 d\u2019aquesta roca es va descobrir a Kariandusi. Kariandusi \u00e9s un assentament que es troba al comtat de Nakuru, a Kenia. Tamb\u00e9 hi ha altres evid\u00e8ncies a altres llocs de l\u2019edat de l\u2019Acheuli\u00e0, al Paleol\u00edtic Inferior (fa uns 1,5 milions d\u2019anys).
\nJaciment de Kariandusi, a Kenia.
\nM\u00e9s tard, tamb\u00e9 es va fer servir l\u2019Obsidiana al Neol\u00edtic. Es valorava molt als nostres avantpassats, a l\u2019Edat de Pedra, ja 7 que podien construir llances o fletxes i donar- l s\u2019hi forma. Amb pedres dures modificaven la seva estructura i la remodelaven al seu gust segons la funci\u00f3 per a la que l\u2019anessin a utilitzar.<\/p>\n

Refer\u00e8ncia bibliogr\u00e0fica<\/strong>
\nhttps:\/\/es.wikipedia.org\/wiki\/Obsidiana<\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Nom: Catal\u00e0: Obsidiana Castell\u00e0: Obsidiana Angl\u00e8s: Obsidian Franc\u00e8s: Obsidienne   Quin tipus i subtipus de roca i\/o mineral \u00e9s? L\u2019 obsidiana \u00e9s una roca volc\u00e0nica, ja que s\u2019ha produ\u00eft per un refredament r\u00e0pid de la lava. Aquesta, pertany al grup dels Silicats, ja que est\u00e0 formada per diferents minerals. Formaci\u00f3 de la roca i\/o mineral: […]<\/p>\n","protected":false},"author":182,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_bbp_topic_count":0,"_bbp_reply_count":0,"_bbp_total_topic_count":0,"_bbp_total_reply_count":0,"_bbp_voice_count":0,"_bbp_anonymous_reply_count":0,"_bbp_topic_count_hidden":0,"_bbp_reply_count_hidden":0,"_bbp_forum_subforum_count":0,"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[1,321],"tags":[323,322],"class_list":["post-2918","post","type-post","status-publish","format-standard","hentry","category-general","category-museu-de-geologia","tag-2a2","tag-magmatiques"],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/wp-json\/wp\/v2\/posts\/2918","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/wp-json\/wp\/v2\/users\/182"}],"replies":[{"embeddable":true,"href":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/wp-json\/wp\/v2\/comments?post=2918"}],"version-history":[{"count":3,"href":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/wp-json\/wp\/v2\/posts\/2918\/revisions"}],"predecessor-version":[{"id":9948,"href":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/wp-json\/wp\/v2\/posts\/2918\/revisions\/9948"}],"wp:attachment":[{"href":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/wp-json\/wp\/v2\/media?parent=2918"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/wp-json\/wp\/v2\/categories?post=2918"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/agora.xtec.cat\/inscaterinaalbert\/wp-json\/wp\/v2\/tags?post=2918"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}