1 10 3 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/3a045ee9b56d4f42ca318e0623d82bac.jpg 9de28fb8f3aa176785607b86ed35a349 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/ad163c9708faad229d3b45dfe05cc6d2.jpg c1d47de48160ed5d95eaa51938891095 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/9a8a6274518a04739a23711773ab19ae.jpg 9d09b58110825fcd56646bf1cec98d2b 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>L172<br /></strong></h2> <h2>Ultramafic cumulate</h2> Subject The topic of the resource <h3>Age</h3> <div class="element-text">Precambrian<br /><br /><h3>Location</h3> <div class="element-text">Lewisian Complex, Dyke<br />Assynt, Sutherland</div> </div> Description An account of the resource <div class="element-set"> <div class="element"> <div class="element-text"> <div class="element"> <div class="element-text five columns omega"> <h3>Hand Specimen</h3> </div> </div> <div class="element"> <div class="element-text five columns omega"> <div class="element-set"> <div class="element"> <div class="element-text">Greenish black, coarse-grained rock, comprising olivine, clinopyroxene and plagioclase.<br />Grains typically 1-2 mm across.<span> </span></div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Olivine<span> </span><br />-<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/256">Subhedral</a><span> </span>to<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/189">euhedral</a><span> </span>grains making up ~45% of the rock.<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/170">Alteration</a><span> </span>to magnetite and serpentine, particularly along the curving cracks. Cracks across the thin-section, could be due to expansion of the rock as the olivine was altered.</p> <p>Clinopyroxene<span> </span><br />-<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/211">Interstitial</a><span> </span>phase making up ~35% of the rock. Moderate<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/247">relief</a>, inclined<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/190">extinction</a> and first order pink to second order orange interference colours.</p> <p>Plagioclase feldspar<span> </span><br />- Interstitial phase making up ~20% of the rock. Low first order interference colours and<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/169">lamellar twinning</a>.</p> <p>Accessory minerals - Biotite, small, interstitial grains, altered.</p> <p>This is a cumulate rock. It has undergone late-stage shear banding.</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text"> <p>Olivine<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/236">phenocrysts</a><span> </span>crystallised first.<span> </span><br />Clinopyroxene grew around the olivine phenocrysts.<span> </span><br />Interstitial feldspar filled in the remaining gaps.<span> </span><br />Shearing of the rock produced bands of deformation.<span> </span><br />Hydrothermal alteration.</p> </div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text">ultramafic cumulate</div> </div> </div> </div> </div> </div> </div> </div> alteration euhedral interstitial shear ultramafic https://wserv3.esc.cam.ac.uk/p1acollections/files/original/8c4e9f36beb5bdf91c3074408b01ccb0.jpg 8d6162debca1ae51b62f6d3fa743c662 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/f5b37535e34701668500f4bbe72bc177.jpg 89547f12b6956f7a89eb9343ae4b2e08 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/7e2698eb1f83d2a13be41526939fc1c4.jpg 92e7719401b0ee848bad92f1f3c3f023 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>L141<br /></strong></h2> <h2>Gabbro</h2> Description An account of the resource <div class="element"> <div class="element"> <div class="element-text five columns omega"> <div class="element"> <h3>Hand Specimen</h3> <div class="element-text">Very dark grey, coarse-grained rock, typical grain size 1-2 mm.<span> </span><br />Main mineral phases are black clinopyroxene, greenish olivine and pale grey feldspar. The rock is cross-cut by a small number of hairline white veins.</div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Plagioclase feldspar<span> </span><br />-<span> </span><a href="/p1acollections/items/show/258">Tabular</a><span> </span>phenocrysts making-up ~50% of the rock. Characteristic<span> </span><a href="/p1acollections/items/show/169">lamellar twinning</a>. Some are<span> </span><a href="/p1acollections/items/show/267">zoned</a>.</p> <p>Olivine<span> </span><br />-<span> </span><a href="/p1acollections/items/show/236">Phenocrysts</a><span> </span>have been extensively altered, rendering them almost unrecognisable. The olivine has decomposed to magnetite and serpentine. Relict olivine grains display characteristic curving cracks and<span> </span><a href="/p1acollections/items/show/189">euhedral</a><span> </span><a href="/p1acollections/items/show/206">form</a>.</p> <p>Clinopyroxene (augite)<span> </span><br />-<span> </span><a href="/p1acollections/items/show/211">Interstitial</a><span> </span>grains making-up ~35% of the rock.<span> </span><a href="/p1acollections/items/show/241">Poikilitic</a><span> </span>texture. Inclined<span> </span><a href="/p1acollections/items/show/190">extinction</a>. Interference colours from first order pink to second order orange. Pale grey under plane polarised light. Some simple twinning.</p> <p>Accessory minerals<span> </span><br />- Opaque, interstitial, probably magnetite.</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text"> <p>Coarse grained → slowly cooled,<span> </span><a href="/p1acollections/items/show/212">intrusive</a>.<span> </span><br />Hydrothermal<span> </span><a href="/p1acollections/items/show/170">alteration</a><span> </span>of olivine after crystallisation of the rock.</p> </div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text">gabbro</div> </div> </div> </div> </div> alteration interstitial intrusive mafic phenocryst https://wserv3.esc.cam.ac.uk/p1acollections/files/original/c79ea7e24906cdc87124323d1c61c679.jpg 2dcf14e8ccd71331a82d77c757769562 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/65cc722b8ca1c5c78563e7830e432ad5.jpg 41095f6476cbd7f3f5fe86f7138c984c https://wserv3.esc.cam.ac.uk/p1acollections/files/original/560ec59ba2f299a27cb59a2103c356ac.jpg ac56cab3922729a7a2da4bfb245672a8 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>L120<br /></strong></h2> <h2>Granodiorite</h2> Subject The topic of the resource <h3>Age</h3> <div class="element-text">Caledonian, Devonian<br /><br /><h3>Location</h3> <div class="element-text">Boulder, Moor of Rannoch</div> </div> Description An account of the resource <div class="element-set"> <div class="element"> <div class="element-text"> <div class="element"> <div class="element-text five columns omega"> <h3>Hand Specimen</h3> </div> </div> <div class="element"> <div class="element-text five columns omega"> <div class="element-set"> <div class="element"> <div class="element-text">Mostly moderately coarse-grained (typically 1-2 mm), some regions finer-grained (typically ~0.5 mm).<span> </span><br />“Salt and pepper” appearance being speckled black and white. Two black phases, biotite mica and hornblende amphibole. White regions comprise quartz and white feldspar.</div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Hornblende amphibole<span> </span><br />- Pleochroic in greens and cream. Some of the grains display<span> </span><a href="/p1acollections/items/show/252">simple twinning</a>. Two<span> </span><a href="/p1acollections/items/show/180">cleavages</a><span> </span>intersect at 56°.</p> <p>Biotite<span> </span><br />-<span> </span><a href="/p1acollections/items/show/256">Subhedral</a><span> </span>to<span> </span><a href="/p1acollections/items/show/173">anhedral</a><span> </span>grains, pleochroic in brown and straw. Straight, speckled<span> </span><a href="/p1acollections/items/show/190">extinction</a>. Chlorite partially replaces biotite – late stage<span> </span><a href="/p1acollections/items/show/170">alteration</a>.</p> <p>Quartz<span> </span><br />- Anhedral,<span> </span><a href="/p1acollections/items/show/211">interstitial</a><span> </span>grains. They display<span> </span><a href="/p1acollections/items/show/263">undulose extinction</a><span> </span>and contain abundant tiny<span> </span><a href="/p1acollections/items/show/210">inclusions</a>, but are characteristically fresh and unaltered.</p> <p>Feldspar, mainly plagioclase<span> </span><br />- Mostly anhedral grains, though some are<span> </span><a href="/p1acollections/items/show/215">lath</a>-shaped. Alteration. Zonation.</p> <p>Accessory minerals:<span> </span><br />- Sphene<span> </span><br />- Magnetite<span> </span><br />- Apatite</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text"> <p>Rock history Hornblende is<span> </span><a href="/p1acollections/items/show/189">euhedral</a>. It is, therefore a primary igneous phase, and must have crystallised from a wet melt.</p> <p>Magma cooled relatively slowly, allowing large crystals to grow.</p> </div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text">granodiorite</div> </div> </div> </div> </div> </div> </div> </div> coarse felsic interstitial