eilifurbjornsson
SENNIL. DÍLÓTT TRAKÝT (porphyritic trachyte - rhomb-porphyry)
Ljósu plöturnar í steininum gætu verið alkalífeldspat-dílar og þá gæti bergið kallast dílótt trakýt. Það er ísúrt til súrt, frekar alkalíríkt berg. Slíkt berg hefur einnig verið kallað "rhomb-porphyry".
Two famous trachyte volcanoes are Mt Kilimanjaro (the highest mountain on the African continent), and Mt Erebus in Antarctica. Trachyte is the volcanic equivalent of syenite. flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/trac...
en.wikipedia.org/wiki/Trachyte
Alkali feldspar - the term alkali means that the mineral contains the metallic elements potassium (K) and / or sodium (Na). flexiblelearning.auckland.ac.nz/rocks_minerals/glossary.h...
Alkali feldspars:
The alkali feldspars are as follows:
orthoclase (monoclinic)[10] LiAlSi3O8,
sanidine (monoclinic)[11] (K,Na)AlSi3O8,
microcline (triclinic)[12] KAlSi3O8,
anorthoclase (triclinic) (Na,K)AlSi3O8.
Sanidine is stable at the highest temperatures, and microcline at the lowest.[10][11] Perthite is a typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many granites can be seen with the naked eye.[13] Microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope.
en.wikipedia.org/wiki/Feldspar#Alkali_feldspars
The most well-known is the rhomb-porphyry from the Oslo Rift in Norway. Similar rocks are known to exist in only two other locations: The East African Rift Valley and the Antarctic1. They are all volcanic areas with active or former (when the rocks formed) continental rifting. www.sandatlas.org/rhomb-porphyry/
SENNIL. DÍLÓTT TRAKÝT (porphyritic trachyte - rhomb-porphyry)
Ljósu plöturnar í steininum gætu verið alkalífeldspat-dílar og þá gæti bergið kallast dílótt trakýt. Það er ísúrt til súrt, frekar alkalíríkt berg. Slíkt berg hefur einnig verið kallað "rhomb-porphyry".
Two famous trachyte volcanoes are Mt Kilimanjaro (the highest mountain on the African continent), and Mt Erebus in Antarctica. Trachyte is the volcanic equivalent of syenite. flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/trac...
en.wikipedia.org/wiki/Trachyte
Alkali feldspar - the term alkali means that the mineral contains the metallic elements potassium (K) and / or sodium (Na). flexiblelearning.auckland.ac.nz/rocks_minerals/glossary.h...
Alkali feldspars:
The alkali feldspars are as follows:
orthoclase (monoclinic)[10] LiAlSi3O8,
sanidine (monoclinic)[11] (K,Na)AlSi3O8,
microcline (triclinic)[12] KAlSi3O8,
anorthoclase (triclinic) (Na,K)AlSi3O8.
Sanidine is stable at the highest temperatures, and microcline at the lowest.[10][11] Perthite is a typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many granites can be seen with the naked eye.[13] Microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope.
en.wikipedia.org/wiki/Feldspar#Alkali_feldspars
The most well-known is the rhomb-porphyry from the Oslo Rift in Norway. Similar rocks are known to exist in only two other locations: The East African Rift Valley and the Antarctic1. They are all volcanic areas with active or former (when the rocks formed) continental rifting. www.sandatlas.org/rhomb-porphyry/