1 10 3 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 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/e3160631658548f9f2dc6e1becea70da.jpg d95ec5a176a934d2c3e57276e230693c https://wserv3.esc.cam.ac.uk/p1acollections/files/original/e2173d02d96267ba32160e6fdf7413e7.jpg 6064d39c4c259244a0f9ee941313b06b https://wserv3.esc.cam.ac.uk/p1acollections/files/original/01845924716bedfe0fd182d669f227cd.jpg 29966d5660a6a3fe8f268bf574236f17 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/16d925108b74372b95b4fdde50676900.jpg 5258ac41a282f9310c3fe1c4115cc800 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/f8b28219498294d826754ab3542fb00f.jpg c99a49a3bc0d2fc2234806df01cd66c1 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/ac59d17b2a65340795a83853876e0422.jpg 27acfdf84cb9a638c01a6ee7daebba0e 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>L102<br /></strong></h2> <h2>Hornblende biotite granite</h2> Subject The topic of the resource <h3>Age</h3> <div class="element-text"> <p>Caledonian, Devonian</p> <h3>Location</h3> <div class="element-text"> <p>Glencoe</p> </div> </div> Description An account of the resource <div class="element-set"> <div class="element"> <div class="element-text"> <div class="element-set"> <div class="element"> <div class="element-text"> <h3><span style="font-size:14px;">Hand Specimen</span></h3> </div> </div> </div> <div class="element-set"> <div class="element"> <div class="element-text"> <p>Medium to coarse-grained rock with a<span> </span><a href="/p1acollections/items/show/203">granular</a><span> </span>texture.<span> </span><br />White feldspar<span> </span><a href="/p1acollections/items/show/215">laths</a><span> </span>2-4 mm long are clearly visible.<span> </span><br />Other phases: pink feldspar, black biotite mica, black hornblende amphibole and pale grey quartz. These grains are more<span> </span><a href="/p1acollections/items/show/188">equant</a>, typically 1-2 mm across.<span> </span><br />Biotite may be distinguished from hornblende by its flaky<span> </span><a href="/p1acollections/items/show/206">habit</a><span> </span>and one good<span> </span><a href="/p1acollections/items/show/180">cleavage</a>. It is shinier than hornblende.</p> </div> </div> <div class="element"> <h3>Thin-section</h3> <div class="element-text"> <p>Plagioclase feldspar<span> </span><br />- The larger laths (2-4 mm long) are strongly<span> </span><a href="/p1acollections/items/show/267">zoned</a>. The cores of these laths, which display clear<span> </span><a href="/p1acollections/items/show/169">lamellar twinning</a>, have been<span> </span><a href="/p1acollections/items/show/232">overgrown</a><span> </span>by rims of more feldspar. Some<span> </span><a href="/p1acollections/items/show/170">alteration</a><span> </span>to white mica.</p> <p>Biotite mica<span> </span><br />- Grains typically 1 mm across. Strongly pleochroic in reddish brown and pale straw. Often associated with small grains of an opaque accessory mineral, probably magnetite.</p> Quartz<span> </span><br />- Grains are 1-2 mm across,<span> </span><a href="/p1acollections/items/show/173">anhedral</a>, and display<span> </span><a href="/p1acollections/items/show/263">undulose extinction</a>. <p>Alkali feldspar<span> </span><br />- Anhedral grains up to 5mm long. Some alteration to white mica. Some grains display a<span> </span><a href="/p1acollections/items/show/228">microperthite texture</a>.</p> <p>Hornblende amphibole<span> </span><br />- Pale green, anhedral. Grains appear to have been “eaten away”, reducing their<span> </span><a href="/p1acollections/items/show/246">prismatic</a><span> </span>form (diamond) to a ragged anhedral<span> </span><a href="/p1acollections/items/show/206">form</a>. Amphiboles have two cleavage planes which intersect at 56°.</p> </div> </div> <div class="element"> <h3>Rock History</h3> <div class="element-text">This coarse-grained rock must have cooled slowly as part of an intrusion.<br /><br />Its granitic composition (essential quartz and feldspar) indicates that it was produced in a continental setting.<br /><br />Strongly zoned plagioclase crystals and “eaten away” appearance of the hornblende could be due to a change in the composition of the liquid from which the phases crystallised; perhaps due to magma mixing or degassing of volatiles from the magma.<span> </span><br /><br />Presence of hornblende and biotite indicate that this is a wet granite, probably from a subduction zone.<br /><br />Hydrothermal alteration of feldspars to white mica.</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, with additional quartz and biotite.</p> </div> </div> <div class="element"> <h3>Rock Name</h3> <div class="element-text"> <p>hornblende biotite granite<br />adamellite</p> </div> </div> </div> </div> </div> </div> arc biotite coarse granite hornblende subduction 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