1 10 10 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/6667ec467cbdbb73c1ac797cbd273fd0.jpg 583f6ed4a44b73689a712abe98dec971 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>Serpentine</h2> Subject The topic of the resource <span>Serpentine is a common alteration product of olivine, produced by hydration at low temperatures.</span> Description An account of the resource <div class="element"> <h3>Formula</h3> <div class="element-text"> <p>Mg₃[Si₂O₅](OH)₄</p> </div> </div> <div class="element"> <h3>Structure</h3> <div class="element-text"> <p>Sheet silicate</p> </div> </div> <div class="element"> <h3>Crystal System</h3> <div class="element-text"> <p><em>Crystal system:</em><span> </span>monoclinic or orthorhombic (-)</p> </div> </div> <div class="element"> <h3>Optical Properties</h3> <div class="element-text"> <p class="NoSpacing"><span>Serpentine is commonly very fine-grained. It can be recognised by its textural association with olivine and by its low birefringence and habit.</span></p> <p class="NoSpacing"><em><span>Colour in plane polarised light:</span></em><span> green</span><span> </span><br class="NoSpacing" /><em><span>Relief:</span></em><span> low</span><span> </span><br class="NoSpacing" /><em><span>Birefringence:</span></em><span> 1^st order</span></p> </div> </div> <div class="element"> <h3>Rock Specimens</h3> <div class="element-text"> <p><a href="/p1acollections/exhibits/show/igneous-rocks/l141">L141 Gabbro</a><span> </span><br /><a href="/p1acollections/exhibits/show/igneous-rocks/l162">L162 Basalt, porphyritic</a><span> </span><br /><a href="/p1acollections/exhibits/show/igneous-rocks/l172">L172 Ultramafic cumulate</a></p> </div> </div> <div class="element"> <h3>Mineral Name</h3> <div class="element-text">serpentine</div> </div> alteration hydration olivine https://wserv3.esc.cam.ac.uk/p1acollections/files/original/696687461afd25ae14285b6fab757bfc.jpg 6283ac65e1ab3970a7982cdbaf1f06d7 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>Chlorite</h2> Subject The topic of the resource <span>Chlorite is a common high-temperature alteration product of ferromagnesian minerals (such as biotite) in igneous rocks. It is stable in the upper part of the crust and is a major constituent of the metamorphic rocks known as greenschists.</span> Description An account of the resource <div class="element-set"> <div class="element"> <div class="element-text"> <h3 class="NoSpacing">Formula</h3> </div> </div> </div> <div class="element-set"> <div class="element"> <div class="element-text">(Mg,Fe²⁺,Fe³⁺,Mn,Al)₁₂[(Si,Al)₈O₂₀](OH)₁₆</div> </div> <div class="element"> <h3>Structure</h3> <div class="element-text"> <p>Sheet silicate</p> </div> </div> <div class="element"> <h3>Crystal System</h3> <div class="element-text"> <p><em>Crystal system:</em><span> </span>monoclinic (+) (-)</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> green</span><span> </span><br class="NoSpacing" /><em><span>Cleavage:</span></em><span> one, good</span><span> </span><br class="NoSpacing" /><em><span>Hardness:</span></em><span> 2-3</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 or green<span> </span><br class="NoSpacing" /><em>Pleochroism:</em><span> </span>weak to moderate<span> </span><br class="NoSpacing" /><em>Relief:</em><span> </span>low<span> </span><br class="NoSpacing" /><em>Birefringence:</em><span> </span>anomalous (blue or brown colours that do not appear in the Michel-Levy chart)<span> </span><br /><em>Extinction:</em><span> </span>straight</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 class="NoSpacing" /><a href="/p1acollections/exhibits/show/igneous-rocks/l101">L101 Granite</a><span> </span><br class="NoSpacing" /><a href="/p1acollections/exhibits/show/igneous-rocks/l120">L120 Granodiorite</a><span> </span><br class="NoSpacing" /><a href="/p1acollections/exhibits/show/igneous-rocks/l130">L130 Andesite, porphyritic (porphyrite)</a><span> </span><br class="NoSpacing" /><a href="/p1acollections/exhibits/show/igneous-rocks/l161">L161 Basalt, amygdaloidal</a><span> </span><br /><a href="/p1acollections/exhibits/show/volcaniclastic-rocks/l201">L201 Tuff</a><span> </span><br /><a href="/p1acollections/exhibits/show/metamorphic-rocks/l504">L504 Garnet schist</a></p> </div> </div> <div class="element"> <h3>Mineral Name</h3> <div class="element-text">chlorite</div> </div> </div> alteration metamorphism https://wserv3.esc.cam.ac.uk/p1acollections/files/original/5eeedf6cef3678833d999dbc34eb9f04.jpg fb5db93c68e1a218f556059b62c702b8 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/e9913f8533b76352e685256738d581d0.jpg 6b88bde6e4c3b3bae18f5133f63d0c5f https://wserv3.esc.cam.ac.uk/p1acollections/files/original/8bc15411d7f18659c4c19c47f51aaed0.jpg 323e29f678447040745639d5408595c0 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>L352<br /></strong></h2> <h2>Limestone, dolomitic</h2> Subject The topic of the resource <h3>Specimen Age</h3> <div class="element-text"> <p>Permian</p> <h3>Location</h3> <div class="element-text"> <p>Sunderland</p> </div> </div> Description An account of the resource <div class="element"> <div class="element"> <h3>Hand Specimen</h3> <div class="element-text"> <p>Pale buff coloured, crystalline rock.<span> </span><br />Numerous cavities, thought to have been formed by shrinkage during<span> </span><a href="/p1acollections/items/show/170">alteration</a><span> </span>of primary calcite (CaCO₃) to secondary dolomite (CaMg[CO₃]₂). There is a weak reaction to dilute acid, which suggests that there may be some calcite remaining.<span> </span><br />Colourless crystalline material infilling holes.</p> </div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text">Almost entirely made up of very fine grains of dolomite (which tends to show more rhomb shaped crystals than calcite).<br />Irregular cavities into which well-developed rhomb crystals of dolomite have grown. Note that one should distinguish between the cavities in the rock (with rhombs of dolomite) and those due to the preparation of the sections.</div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text">It is thought that this rock was initially made-up of calcite. The alteration from calcite to dolomite, with its consequent increase in specific gravity and decrease in volume, accounts for the formation of the cavities.</div> </div> <div class="element"></div> <div class="element"></div> <div class="element"> <h3>Rock Name</h3> <div class="element-text">dolmitic limestone<br />dolomite<br />magnesian limestone</div> </div> </div> alteration 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/852a77355d6e4e7f6cf8052de0bf7a9d.jpg 3418fba1e4453736b6dbd51d55fd9583 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/aab79550a27397bff8be8a5cb67ef43f.jpg f5f51d065ee3cc8e993e930077cbd5fc https://wserv3.esc.cam.ac.uk/p1acollections/files/original/1c200ce8cf23f154e881c3c62ad865c8.jpg 25a8c42f179836492f49a6fdb0bcbb5f https://wserv3.esc.cam.ac.uk/p1acollections/files/original/f3204ba875eb0b5fb7aaffafd6e91261.jpg 6a3a28ccf49c7653bc57780b5eacdd11 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/57c910796611238dbf565e32ca5fc702.jpg d53f7084c610e651bdaf2389f9297e28 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>L162<br /></strong></h2> <h2>Basalt, porphyritic</h2> Subject The topic of the resource <h3>Specimen Age</h3> <div class="element-text"> <p>Carboniferous</p> <h3>Location</h3> <div class="element-text"> <p>Volcanic neck, Lion's Haunch, Arthur's Seat, Edinburgh</p> </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"> <div class="element-text"> <div class="element-text"> <div class="element"> <div class="element-text five columns omega"> <div class="element"> <div class="element-text five columns omega"></div> </div> <div class="element"> <div class="element-text five columns omega"> <div class="element-set"> <div class="element"> <div class="element-text"> <h3>Hand Specimen</h3> </div> </div> </div> <div class="element-set"> <div class="element"> <div class="element-text"> <p>Black,<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/244">porphyritic</a><span> </span>rock comprising black clinopyroxene, grey feldspar and greenish olivine<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/236">phenocrysts</a>, in a fine-grained<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/205">groundmass</a>.</p> </div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Plagioclase feldspar<span> </span><br />- Phenocrysts 1-4mm long, with a euhedral,<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/258">tabular</a><span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/206">form</a>. Randomly orientated. Characteristic<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/169">lamellar twinning</a>. Some are<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/267">zoned</a>.<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/210">Inclusions</a><span> </span>of magnetite, clinopyroxene and other minerals. Extensive<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/170">alteration</a><span> </span>along abundant cracks.</p> <p>Clinopyroxene (augite)<span> </span><br />-<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/189">Euhedral</a><span> </span>phenocrysts, 1-2 mm across. 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><span> </span>and first order pink to second order orange interference colours. Pale pink in thin-section. Some are<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/267">zoned</a>.</p> <p>Olivine<span> </span><br />- Very few phenocrysts are fresh enough to be easily identifiable. These are colourless in plane polarised light, have moderate relief, and up to second order pink interference colours. No<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/180">cleavage</a>.</p> <p>- 1st phase of alteration along cracks: The majority of the phenocrysts have been completely altered to greenish serpentine.</p> <p>- 2nd phase of alteration: orange brown mineral – probably the amphibole<span> </span><span>cummingtonite</span>. Characteristic curving cracks and the<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/246">prismatic</a><span> </span>form of olivine are still visible.</p> <p>Groundmass<span> </span><br />- Fine-grained. Plagioclase feldspar needles, clinopyroxene, some olivine (mostly altered), and opaques, probably magnetite. Occasional calcite grain.</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text"> <p>Two stage cooling<span> </span><br />1. Phenocrysts grow slowly in a magma chamber.<span> </span><br />2. Fine-grained groundmass grew rapidly →<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/191">extrusive</a>.<span> </span><br />Hydrothermal alteration, possibly as part of the<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/266">volcanic</a><span> </span>pile.</p> </div> </div> <div class="element"> <h3>Advanced Notes</h3> <div class="element-text"><span>Cummingtonite</span><span> </span>is an amphibole. It is colourless to pale green in thin-section, has moderate relief and two cleavages which intersect at 56°.</div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text">porphyritic basalt</div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> alteration extrusive volcanic https://wserv3.esc.cam.ac.uk/p1acollections/files/original/6ee5b4daa895a80c4f5d1219f546fd1f.jpg ec992c8fa5fc180cef9aa183c5fccb0b https://wserv3.esc.cam.ac.uk/p1acollections/files/original/f04b282ccc316fc1d49d4170730b5892.jpg 7759e3afb21758ccf4ccadb89eb40ce9 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/d5a2b07e623f5f5b39a9506ee7ac050f.jpg 41972d8ec488fd6c039ae81709eaf2e3 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>L161<br /></strong></h2> <h2>Basalt, amygdaloidal</h2> Subject The topic of the resource <h3>Specimen Age</h3> <div class="element-text"> <p>Cenozoic</p> <h3>Location</h3> <div class="element-text"> <p>Lava, Skye</p> </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"> <div class="element-text"> <div class="element-text"> <div class="element"> <div class="element-text five columns omega"> <div class="element-text"> <div class="element-text"></div> </div> </div> </div> <div class="element"> <div class="element-text five columns omega"> <div class="element-set"> <div class="element"> <div class="element-text"> <h3>Hand Specimen</h3> </div> </div> </div> <div class="element-set"> <div class="element"> <div class="element-text"> <p>Fine-grained, greenish black rock comprising dark and white minerals.<span> </span><br />Contains<span> </span><a href="/p1acollections/items/show/172">amygdales</a>, mostly white, though some have black cores.</p> </div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Fine-grained plagioclase<span> </span><a href="/p1acollections/items/show/215">laths</a><span> </span>and irregular clinopyroxene (augite) grains, replaced with calcite. Many of the plagioclase laths have been almost entirely altered.</p> <p>The amygdales are filled with<span> </span><span>zeolite</span>, growing in spherulitic and radiate patterns. Many have rims of calcite and fine-grained chlorite.</p> <p>Some vein material -<span> </span><a href="/p1acollections/items/show/203">granular</a><span> </span>quartz with<span> </span><a href="/p1acollections/items/show/257">sutured contacts</a>.</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text"> <p>Fine-grained → rapid,<span> </span><a href="/p1acollections/items/show/191">extrusive</a><span> </span>crystallisation.<span> </span><br />Gas bubbles trapped within lava produced<span> </span><a href="/p1acollections/items/show/264">vesicles</a>.<span> </span><br />Circulation of fluids → precipitation of zeolite within the vesicles.</p> </div> </div> <div class="element"> <h3>Advanced Notes</h3> <div class="element-text"> <p><span>Zeolites</span><span> </span>are produced at low temperatures. They are commonly precipitated in basaltic volcanic piles.</p> </div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text">amygdaloidal basalt</div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> </div> alteration extrusive mafic 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/7b7f1ba53fca171d08e85f7165d1330d.jpg 3f0131a7e6802310254284a8c2b5dedb https://wserv3.esc.cam.ac.uk/p1acollections/files/original/a80c30b1e44c57fd7e5cd8ccb0e22649.jpg 324282e4d846cb1d25996476c51bf0ac https://wserv3.esc.cam.ac.uk/p1acollections/files/original/d0b428c197fabf498b5cc2789834ede6.jpg c32bf03df5c51ff80285c039ec70939e 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>L130<br /></strong></h2> <h2>Andesite, porphyritic (porphyrite)</h2> Subject The topic of the resource <h3>Age</h3> <div class="element-text"> <p>Early Paleozoic</p> <h3>Location</h3> <div class="element-text"> <p>Cansip Porphyry Sills<br />Sutherland</p> </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"> <div class="element"> <div class="element-text five columns omega"> <div class="element-text"> <div class="element-text"></div> </div> </div> </div> <div class="element"> <div class="element-text five columns omega"> <div class="element-set"> <div class="element"> <div class="element-text"> <h3>Hand Specimen</h3> </div> </div> </div> <div class="element-set"> <div class="element"> <div class="element-text"> <p><a href="/p1acollections/items/show/244">Porphyritic</a>.<span> </span><br />Large,<span> </span><a href="/p1acollections/items/show/258">tabular</a>, pale grey-yellow<span> </span><a href="/p1acollections/items/show/236">phenocrysts</a><span> </span>of plagioclase feldspar, randomly oriented, twin striations are visible on many of them.<span> </span><br />Pink-brown<span> </span><a href="/p1acollections/items/show/184">cryptocrystalline</a><span> </span>groundmass contains black, shiny flakes of biotite.</p> </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/189">Euhedral</a><span> </span>phenocrysts, 2-20 mm long, displaying the characteristic<span> </span><a href="/p1acollections/items/show/169">lamellar twinning</a>. Some<span> </span><a href="/p1acollections/items/show/170">alteration</a><span> </span>to white mica. In places they have been replaced by chlorite and calcite.</p> <p>Biotite<span> </span><br />- Phenocrysts, most &lt;1mm long, with characteristic brown to pale straw pleochroism and straight<span> </span><a href="/p1acollections/items/show/190">extinction</a>.</p> <p>Accessory minerals<span> </span><br />- Quartz<span> </span><br />- Apatite</p> <p>Groundmass<span> </span><br />- Mainly cryptocrystalline. A small number of feldspar grains can be identified. Small ragged<span> </span><a href="/p1acollections/items/show/264">vesicles</a>.</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text"> <p>Two-stage cooling: phenocrysts followed by<span> </span><a href="/p1acollections/items/show/205">groundmass</a>.<span> </span><br />Phenocrysts are euhedral indicating that they crystallised free-floating in a magma chamber.<span> </span><br />The fine-grained groundmass must have crystallised rapidly due to cooling at the Earth’s surface.<span> </span><br />Alteration occurred after crystallisation.</p> </div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text">porphyritic andesite<br />porphyrite</div> </div> </div> </div> </div> </div> </div> </div> </div> </div> alteration groundmass phenocryst porphyritic 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/744797d8340f3fb3bb5223f8d6e813df.jpg 2216573b7943b4d2108e89ba7c1ae3ee https://wserv3.esc.cam.ac.uk/p1acollections/files/original/6ca84b87271026626b96c159bfd42604.jpg 5fed78d37132afb7111530b3f05d4631 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/6e5325c5d9551839979a6bc06bdf7a19.jpg d843ba39bcd4aa3e3a92b6b8306412a7 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>L101<br /></strong></h2> <h2>Granite</h2> Subject The topic of the resource <h3><strong>Age</strong></h3> Caledonian, Devonian<br /><br /><h3><strong> Location</strong></h3> Shap Fell, Cumbria Description An account of the resource <div class="element-set"> <div class="element"> <div class="element-text"> <h3 class="element-set"><strong>Hand</strong> Specimen</h3> <div class="element-set"> <div class="element"> <div class="element-text"> <p>Coarse-grained,<span> </span><a href="/p1acollections/items/show/244">porphyritic</a><span> </span>texture.<span> </span><br /><a href="/p1acollections/items/show/236">Phenocrysts</a><span> </span>of pink feldspar, 10-30 mm long,<span> </span><a href="/p1acollections/items/show/258">tabular</a>, display clear<span> </span><a href="/p1acollections/items/show/180">cleavage</a> planes.<span> </span><br /><a href="/p1acollections/search?query=groundmass&amp;query_type=keyword&amp;record_types%5B%5D=Item&amp;record_types%5B%5D=File&amp;record_types%5B%5D=Collection&amp;record_types%5B%5D=Exhibit&amp;record_types%5B%5D=ExhibitPage&amp;record_types%5B%5D=SimplePagesPage&amp;submit_search=Search">Groundmass</a><span> </span>of coarse-grained white feldspar, pink feldspar, quartz and biotite.<span> </span><br />Quartz grains are<span> </span><a href="/p1acollections/items/show/173">anhedral</a><span> </span>and display their characteristic<span> </span><a href="/p1acollections/items/show/182">conchoidal fracture</a><span> </span>and<span> </span><a href="/p1acollections/items/show/265">vitreous lustre</a>.</p> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Alkali feldspar (orthoclase)<span> </span><br />- Pink phenocrysts up to ~10 mm long, relatively fresh (unaltered).</p> <p>Groundmass<span> </span><br />- Feldspar (both plagioclase and alkali) grains 1-4mm long, mainly<span> </span><a href="/p1acollections/items/show/256">subhedral</a>, though some are quite<span> </span><a href="/p1acollections/items/show/215">lath</a><span> </span>shaped. Partially altered. The plagioclase grains display their characteristic<span> </span><a href="/p1acollections/items/show/169">lamellar twinning</a>.<span> </span><br />- Biotite grains (0.5-2 mm) with subhedral to anhedral<span> </span><a href="/p1acollections/items/show/206">form</a>. Grains have ragged edges and are partially altered to chlorite, mainly along<span> </span><a href="/p1acollections/items/show/180">cleavage</a><span> </span>planes.<span> </span><br />- Quartz grains (typically 2-5 mm) contain lots of tiny<span> </span><a href="/p1acollections/items/show/210">inclusions</a><span> </span>and display<span> </span><a href="/p1acollections/items/show/263">undulose extinction</a>.</p> <p>Accessory minerals<span> </span><br />- Sphene<span> </span><br />- Apatite<span> </span><br />- Opaque mineral</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text"> <p>Porphyritic texture means this rock underwent two stages of cooling; phenocrysts crystallised first followed by the groundmass. The groundmass is coarse-grained, and must have crystallised slowly as part of an intrusion.</p> <p>Plagioclase and alkali feldspar both occur in this rock, indicating that it formed at high pressures.</p> <p>Granitic composition (essential quartz and feldspar) indicates that it was produced in a continental setting. Late-stage<span> </span><a href="/p1acollections/items/show/170">alteration</a>.</p> </div> </div> <div class="element"> <h3>Advanced Notes</h3> <div class="element-text"> <p>This rock is classified as an<span> </span><span>adamellite</span><span> </span>because it contains roughly equal proportions of alkali feldspar and plagioclase feldspar, as well as biotite and quartz.</p> </div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text"> <p>granite<br />adamellite</p> </div> </div> </div> </div> </div> </div> </div> </div> alkali alteration feldspar