Chromite is a spinel-type mineral, like magnetite, and has an extensive solid solution in the magnetite composition direction. If a mineral commonly has a range of colours, it will appear once for each colour. Chromite is dark-brown to opaque at full thin section thickness. In thin section this rock contains orthoclase feldspar laths which exhibit simple twinning, slightly higher relief and dusty grains of nepheline, phlogopite mica which is pleochroic in dark brown to straw yellow, and rare melanite garnet. ... Nepheline (KNa 3 Al 4 Si 4 O 16) (along with the variety known as eleolite) is the most widespread of all feldspathoids. This optical mineralogy/petrography video is part of the "video atlas of minerals in thin section" library at https://www.rockptx.com. Photomicrograph of thin section showing glomeroporphyritic texture defined by plagioclase and clinopyroxene grains embedded in fine-grained groundmass of porphyritic basalt. To link to this object, paste this link in email, IM or document To embed this object, paste this HTML in website. Plagioclase Feldspar (thin section) View Description. Add tags Comment Rate. Within the tables, minerals are arranged by colour so as to help with identification. This optical mineralogy/petrography video is part of the "video atlas of minerals in thin section" library at https://www.rockptx.com. Nepheline - Na 3 (Na,K)[Al 4 Si 4 O 16] Nepheline, also called nephelite (from Greek "cloud"), is a feldspathoid: a silica-undersaturated aluminosilicate. Cr-Mg-Al-rich chromites are realtively transparent, and can be dark-brown at full thin section thickness. This slide is mainly nepheline and K-feldspar, both in large and clear phenocrysts with interesting textures, with pleochroic aegirine and cancrinite. Nepheline is the most common mineral variety in a very complex group of polymorphs ranging from NaAlSiO 4 (Nepheline) to KAlSiO 4 (kalsilite). This is a thin section of a Nepheline Syenite from an unknown source, but probably Kola. Home Rocks and Minerals Plagioclase Feldspar (thin section) Reference URL Share . Identification Tables for Common Minerals in Thin Section These tables provide a concise summary of the properties of a range of common minerals.
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