SUPPORT US. If is important to you, click here to donate to our Fall 2019 fundraiser!
Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat ArticlesThe ElementsBooks & Magazines
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsUsersMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryMineral Photography

Identity HelpPseudomorphose: What after what?

11th Sep 2019 21:53 BSTManuel Maia

Opinions about this  sample are very welcome!
Loose "cube" self-collected on the margins of  Caniçada barrage (Nort of Portugal) in the late 90's
Dimensions: +/- 1 cm edge

11th Sep 2019 22:09 BSTRalph Bottrill Manager

It looks like a feldspar porphyry that has accidentally broken into a cubic shape due to natural jointing?

11th Sep 2019 22:59 BSTPaul Brandes Manager

What about a rhyolite porphyry?

12th Sep 2019 09:24 BSTRalph Bottrill Manager

Quite likely, but feldspar porphyry also allows for it potentially being a dacite etc.; you could check if the phenocrysts are Kspar, plag, quartz etc.
Mineral and/or Locality is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © and the Hudson Institute of Mineralogy 1993-2019, except where stated. Most political location boundaries are © OpenStreetMap contributors. relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: September 16, 2019 22:05:01
Go to top of page