K Feldspar Thin Section
K Feldspar Jpg 620 380
Tartan Twinning In Alkali Feldspar In A Granite Rocks And Minerals Microscopic Photography Geology
Related Image Fabric Textures Feldspar Texture
Thin Section Geology Mineralogy Rocks And Minerals
Thinsectionthursday Thin Section Microphotograph And Sem Image Of The Notikewan Formation Showing Secondary Dissolution Porosity O Porosity Oil And Gas Image
Geology Geology Rocks Minerals
This mineral is often called potassium feldspar or k feldspar because potassium always exceeds sodium in its formula.
K feldspar thin section. To highlight k feldspar switch to a medium or low magnification objective usually 4 or 10x works well mostly close the substage iris and raise the stage slightly yes raise. Adularia is a k feldspar produced by low. Colourless often cloudy low relief low order interference colours polysynthetic twins microcline simple twins sanidine orthoclase exsolution lamellae orthoclase and microcline common minerals that might be confused with k feldspar and occur in similar rocks.
Microcline is a triclinic k feldspar and has a characteristic cross hatched tartan pattern of twinning seen with a petrographic microscope. Microcline is the stable form below about 400 c. In thin section microcline orthoclase and sanidine are distinguished by their twinning optical sign and 2vo.
Orthoclase and sanidine are stable above 500 c and 900 c respectively. Sanidine is usually distinguished rather easily from the other alkali feldspars because it typically appears glassy i e it tends to be colourless and much of it is transparent. In general keys to identifying k feldspar are its lack of color its low birefringence and its twinning.
The ideal value for the potassium rich alkali feldspars is 2 56 which is less than the lowest value for the plagioclases namely 2 62 for albite. All three minerals have the same formula they re polymorphs but in thin section they vary a bit. Some of the properties will be the same across the board but i ll try and highlight the differences.
In plane light the k feldspars are very very similar to quartz. Potassium feldspar comes in three different crystal structures that depend on the temperature it formed at. Orthoclase and sanidine are both optically monoclinic k feldspars.
Key optical features of k feldspar in thin section. Add tags comment rate. In thin section alkali feldspar grains often look like they re sprinkled with dirt ppl or tiny confetti xpl.
Alkali Feldspar In Ppl Showing Perthitic Texture Low Relief Colorless Basically Invisible Feldspar Optical Microscope Too Thin
Coarse Feldspathic Sandstone Torridon Group Torridonian Xpl There Is Quartz E G Large Grain At Left Potassium Feldspar With Tartan Geology Rock Gneiss
Several K Feldspar Porphyroclasts In Ultramylonitic Matrix Composed Of Quartz Mica Feldspar Asymmetric Tails Of Recrystallized Geology Rock Textures Minerals
Minerals Under The Microscope Feldspar Minerals Crystals
Alkali Feldspar Showing Perthitic Texture From Exsolution Of Na And K Feldspar These Stringers Are Coarser Than Geology Fabric Textures Materials Engineering
Gabbro Thin Section Www Soest Hawaii Edu Soest Facilities Lapidary Patterns In Nature Geology Nature Art
Anorthite Thin Section Xpl X10 Geologia
Perthite Unmixing In Microcline Xpl Image 10x Field Of View 2mm Geology Metamorphic Rocks Igneous
Amphibole In Ppl Geology Crystals Minerals Mineralogy
Andalusite In Ppl Showing Distinctive Chiastolite Cross Metamorphic Metamorphic Rocks Geology
Sigma S Porphyroclast Orthose In A Mylonitic Granite From Khumbu Nepal Xpl Image 2x Field Of View 7mm Rocas Minerales
Olivine Partially Altered In Serpentine Note The Radial Fracture Due To Increases Of Volume For Serpentinization Ppl Geology Nature Inspiration Paleontology
Geology And Radioactivity Of The Basement Rocks Of Wadi El Sahu Area Southwestern Sinai Egypt Geology Sedimentary Rocks Plate Tectonics
