1 10 2 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/d1bcada3b82f04f017d8a0e8b86f72b3.jpg 132f0e00763d982d7b38233c335bea76 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/f7281678c485abb0e71780e0b9119a47.jpg cbe05af402dff631ae66cc0a04916568 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/a7983a9ced24e5578ce7e9e61cac9c9c.jpg d1374b7286c25297bfe7fa333bd490d0 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><strong>L110<br /></strong></h2> <h2>Rhyolite, porphyritic (quartz porphyry)</h2> Subject The topic of the resource <h3>Age</h3> <div class="element-text"> <p>Ordovician</p> <h3>Location</h3> <div class="element-text"> <p>Armboth Dyke <br />Thirlmere, Cumbria</p> </div> </div> Description An account of the resource <div class="element"> <h3>Hand Specimen</h3> <div class="element-text"> <p>Pink-brown,<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/244">porphyritic</a><span> </span>rock with a very fine-grained<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/205">groundmass</a>.<span> </span><br />Abundant pink<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/221">macrocrysts</a><span> </span>(5-10 mm).<span> </span><br /><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/236">Phenocrysts</a><span> </span>of feldspar (2-4 mm) and quartz (2-4 mm).<span> </span><br />Accessory black mineral.</p> </div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Quartz<span> </span><br />- Rounded phenocrysts (1-4 mm) with embayments/cavities and tiny<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/210">inclusions</a>.</p> <p>Feldspar<span> </span><br />- Phenocrysts ~2mm,<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/256">subhedral</a>. Mainly alkali feldspar, some plagioclase.<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/170">Alteration</a> to white mica.</p> <p>Garnet<span> </span><br />- Very rare,<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/189">euhedral</a><span> </span>phenocrysts (0.5-1 mm).<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/213">Isotropic</a>, high<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/247">relief</a>, colourless to pale pink.</p> <p>Biotite<span> </span><br />- Very rare fragments with chlorite alteration.</p> <p>Groundmass<span> </span><br />-<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/227">Microcrystalline</a><span> </span>quartz and feldspar, with some muscovite and biotite.</p> <p>Calcite<span> </span><br />- Some of the feldspars phenocrysts and most of the garnet phenocrysts have been replaced by calcite. These are the pink macrocrysts visible in hand specimen.</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text">Porphyritic texture indicates two-stage cooling. The phenocrysts grew slowly in a magma chamber; the fine-grained groundmass formed during rapid cooling at the Earth’s surface.<br /><br />Late stage hydrothermal alteration to white mica and carbonate.</div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text">porphyritic rhyolite<br />quartz porphyry</div> </div> alteration inclusions porphyritic https://wserv3.esc.cam.ac.uk/p1acollections/files/original/f05e63c01d867dcb78bad17121fd1d31.jpg 2d73462e69c78971d66f92dd5d6e622b https://wserv3.esc.cam.ac.uk/p1acollections/files/original/8a6e1a596d0d3bc7ae44e61aab691d56.jpg 84814d5a6509f76521cd808580d14224 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/4b619fdf5cbd3e05bf7ad22b3494cef3.jpg bdc304f5ffbdb6cb553489a47568c9ca 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><strong>L100<br /></strong></h2> <h2>Alkali granite</h2> Subject The topic of the resource <h3>Specimen Age</h3> <p>Variscan , Permo-Carboniferous</p> <h3></h3> Description An account of the resource <h3><span style="font-size:14px;">Hand Specimen</span></h3> <div class="element-set"> <div class="element"> <div class="element-text"> <p>This rock has a<span> </span><a href="/p1acollections/items/show/244">porphyritic</a><span> </span>texture.<span> </span><a href="/p1acollections/items/show/236">Phenocrysts</a><span> </span>of white feldspar up to 30mm long are surrounded by a coarse<span> </span><a href="/p1acollections/items/show/205">groundmass</a><span> </span>of quartz, biotite and white feldspar.</p> </div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Alkali feldspar (orthoclase)<span> </span><br />- Grains typically 2-4mm long,<span> </span><a href="/p1acollections/items/show/256">subhedral</a><span> </span>to<span> </span><a href="/p1acollections/items/show/173">anhedral</a>, dirty looking due to<span> </span><a href="/p1acollections/items/show/170">alteration</a>. Many display a<span> </span><a href="/p1acollections/items/show/228">microperthite texture</a>.</p> <p>Plagioclase feldspar<span> </span><br />- Grains typically 1-4mm long, subhedral, characteristic<span> </span><a href="/p1acollections/items/show/169">lamellar twinning</a>. Many of the grains look “dirty” under plain polarised light, and have high<span> </span><a href="/p1acollections/items/show/177">birefringence</a><span> </span>speckles under cross-polarised light. They have been partially altered to white mica. Some grains are<span> </span><a href="/p1acollections/items/show/267">zoned</a>.</p> <p>Quartz<span> </span><br />- Grains typically 1-4mm across, anhedral. They are characteristically clean and unaltered when compared with feldspar grains, but do contain many tiny<span> </span><a href="/p1acollections/items/show/210">inclusions</a>.</p> <p>Biotite<span> </span><br />- Grains similar size as the rest of the<span> </span><a href="/p1acollections/items/show/205">groundmass</a>. Strongly<span> </span><a href="/p1acollections/items/show/239">pleochroic</a><span> </span>in pale straw and dark reddish brown. Speckled<span> </span><a href="/p1acollections/items/show/190">extinction</a>. Some sections show the one good<span> </span><a href="/p1acollections/items/show/180">cleavage</a><span> </span>of biotite. Small black blobs and circles are dotted all over the crystals. These are<span> </span><a href="/p1acollections/items/show/238">pleochroic haloes</a>, produced by zircons. Partially decomposed to chlorite.</p> <p>Accessory minerals<span> </span><br />- Apatite<span> </span><br />- Small irregular grains of muscovite mica</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text">This is a coarse-grained rock, which must have cooled slowly as part of an intrusion. Its granitic composition (essential quartz and feldspar) indicates that it was produced in a continental setting.</div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text">alkali granite</div> </div> </div> coarse continental felsic inclusions