1 10 1 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/7eda87156991f7c8b27a0e8510940358.jpg 2635d861ca5b4c2cbbd828726c95bfd4 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/dcc7eadcc1e8adacfb3ca0062cf15b41.jpg 35dd6efe13e1fca981d0837a56294e0b https://wserv3.esc.cam.ac.uk/p1acollections/files/original/4df0492facb5854e9375d2f627f192fe.jpg ffc9075681e5de8a163ba2009ad46bb1 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/52688639ee0b849fb604e43c822c434b.jpg 27a1d7561ed102f3dc1de4996962dd8d Physical Object An inanimate, three-dimensional object or substance. Note that digital representations of, or surrogates for, these objects should use Moving Image, Still Image, Text or one of the other types. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource <h2>Alkali feldspar</h2> Description An account of the resource <div class="element"> <div class="element"> <h3>Formula</h3> <div class="element-text"> <p>(K,Na)[AlSi₃O₈]</p> </div> </div> <div class="element"> <h3>Structure</h3> <div class="element-text"> <p>Framework silicate</p> </div> </div> <div class="element"> <h3>Crystal System</h3> <div class="element-text"> <p><em>Crystal system:</em><span> </span>monoclinic (-) or triclinic (+) (-)</p> </div> </div> <div class="element"> <h3>Physical Properties</h3> <div class="element-text"> <p class="NoSpacing"><em><span>Colour in hand specimen:</span></em><span> white or pink</span><span> </span><br class="NoSpacing" /><em><span>Cleavage:</span></em><span> two at 90°</span><span> </span><br class="NoSpacing" /><em><span>Hardness:</span></em><span> 6-6.5</span></p> </div> </div> <div class="element"> <h3>Optical Properties</h3> <div class="element-text"> <p class="NoSpacing"><em>Colour in plane polarised light:</em><span> </span>colourless<span> </span><br class="NoSpacing" /><em>Pleochroism:</em><span> </span>none<span> </span><br class="NoSpacing" /><em>Relief:</em><span> </span>low<span> </span><br class="NoSpacing" /><em>Birefringence:</em><span> </span>~0.008; 1^st<span> </span>order greys<span> </span><br class="NoSpacing" /><em>Extinction:</em><span> </span>inclined<span> </span><br class="NoSpacing" /><em>Twinning: </em>usually simple or lamellar;<span> </span><br />              Microcline (KAlSi₃O₈) displays characteristic cross-hatched twinning</p> </div> </div> <div class="element"> <h3>Mineral Specimens</h3> <div class="element-text"> <p class="NoSpacing"><strong><span>M400 </span></strong><strong><span>Alkali feldspar, microcline</span></strong><span> </span><br class="NoSpacing" />A single crystal of pale orange-pink alkali feldspar.<span> </span><br class="NoSpacing" />Pearly lustre.</p> <p class="NoSpacing"><strong><span>M401 </span></strong><strong><span>Alkali feldspar, orthoclase</span></strong><span> </span><br class="NoSpacing" /><strong>Norway</strong><strong></strong><span> </span><br class="NoSpacing" />A fragment of opaque, pale grey alkali feldspar.<span> </span><br class="NoSpacing" />Two sets of good cleavage at right angles, with a pearly lustre on the cleavage faces.</p> <p class="NoSpacing"><strong><span>M402 </span></strong><strong><span>Alkali feldspar, orthoclase</span></strong><span> </span><br class="NoSpacing" /><strong>Shap, Westmorland</strong><span> </span><br class="NoSpacing" />Porphyritic granite.<span> </span><br class="NoSpacing" />Large phenocrysts of pink feldspar, two sets of cleavage at 90°, simple twinning.<span> </span><br class="NoSpacing" />Also white plagioclase feldspar, quartz and biotite<strong>.</strong></p> </div> </div> <div class="element"> <h3>Rock Specimens</h3> <div class="element-text"> <p><a href="/p1acollections/exhibits/show/igneous-rocks/l100">L100 Alkali granite</a><span> </span><br /><a href="/p1acollections/exhibits/show/igneous-rocks/l101">L101 Granite</a><span> </span><br /><a href="/p1acollections/exhibits/show/igneous-rocks/l102">L102 Hornblende biotite granite</a><span> </span><br /><a href="/p1acollections/exhibits/show/igneous-rocks/l110">L110 Rhyolite, porphyritic (quartz porphyry)</a></p> </div> </div> <div class="element"> <h3>Mineral Name</h3> <div class="element-text">alkali feldspar</div> </div> </div> felsic granite rhyolite