23 10 264 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/. Description An account of the resource This glossary describes a number of geological terms with which the 1A students should become familiar.<span> It is by no means an exhaustive list, but is aimed to help you understand the material within the first year course.</span> Title A name given to the resource Glossary 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>Permeability</h2> Subject The topic of the resource <p>The ability of a material to allow fluids to pass through it. A permeable material contains an interconnected system of channels though which fluids can diffuse. An impermeable material does not allow fluids to diffuse through it, either because it has no porosity, or because its porosity is unconnected.</p> Description An account of the resource <em>Compare with<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/243">porosity</a>.</em> 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/. Description An account of the resource This glossary describes a number of geological terms with which the 1A students should become familiar.<span> It is by no means an exhaustive list, but is aimed to help you understand the material within the first year course.</span> Title A name given to the resource Glossary 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>Phaneritic</h2> Description An account of the resource <em>See<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/203">granular</a>.</em> 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/. Description An account of the resource This glossary describes a number of geological terms with which the 1A students should become familiar.<span> It is by no means an exhaustive list, but is aimed to help you understand the material within the first year course.</span> Title A name given to the resource Glossary 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>Phenocryst</h2> Subject The topic of the resource <span>Phenocrysts are igneous crystals which have grown in the magma that they are found within. They are large crystals, visible to the naked eye. Importantly, they are significantly larger than the surrounding crystals of the groundmass.</span> Description An account of the resource Compare with <a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/221">macrocryst</a> and <a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/245">porphyroblast</a>. https://wserv3.esc.cam.ac.uk/p1acollections/files/original/2f7362a5c5cc5e00bc17ca856238ee37.jpg 44db79a97ef535c74d897e9db008bca0 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/94761134fac46b7078906210b5bb3b8f.jpg 323c8b77db6400b701b97ff8bcaa92f2 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/de6097beca8b60a758b218148982f48d.jpg cc38a8962e52d9ea6bf655b0c40038cd 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>Plagioclase feldspar</h2> Description An account of the resource <div class="element"> <h3>Formula</h3> <div class="element-text"> <p>Na[AlSi₃O₈] – Ca[Al₂Si₂O₈]</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>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</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>~0.010, 1^st<span> </span>order grey<span> </span><br class="NoSpacing" /><em>Extinction:</em><span> </span>inclined<span> </span><br class="NoSpacing" /><em>Twinning:</em><span> </span>lamellar, very common</p> </div> </div> <div class="element"> <h3>Mineral Specimens</h3> <div class="element-text"> <p class="NoSpacing"><strong><span>M403 </span></strong><strong><span>Plagioclase feldspar, oligoclase</span></strong><span> </span><br class="NoSpacing" /><strong>Ytterby</strong><strong>, Sweden</strong><strong></strong><span> </span><br class="NoSpacing" />A cleavage fragment of white plagioclase feldspar<span> </span><br class="NoSpacing" />Pearly lustre on cleavage planes<span> </span><br class="NoSpacing" />Two sets of cleavage at 90°<span> </span><br class="NoSpacing" />Fine parallel striations due to lamellar twinning</p> <p class="NoSpacing"><strong><span>M404 </span></strong><strong><span>Plagioclase feldspar, labradorite</span></strong><span> </span><br class="NoSpacing" /><strong>Labrador</strong><strong></strong><span> </span><br class="NoSpacing" />Dark grey, light where fragments are small due to cracking along cleavage<span> </span><br class="NoSpacing" />Schiller (blue iridescence), characteristic of labradorite<span> </span><br class="NoSpacing" />Very fine parallel striations due to lamellar twinning</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/l112">L112 Rhyolite</a><span> </span><br /><a href="/p1acollections/exhibits/show/igneous-rocks/l120">L120 Granodiorite</a><span> </span><br /><a href="/p1acollections/exhibits/show/igneous-rocks/l130">L130 Andesite, porphyritic (porphyrite)</a><span> </span><br /><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><span> </span><br /><a href="/p1acollections/exhibits/show/metamorphic-rocks/l504">L504 Garnet schist</a></p> </div> </div> <div class="element"> <h3>Advanced Notes</h3> <div class="element-text"> <p class="NoSpacing"><span>Plagioclase feldspar forms a continuous solid solution between the sodic endmember (albite, or Ab) and the calcic endmember (anorthite, or An). The series is sub-divided into albite (An_0-10), oligoclase (An_10-30) andesine (An_30-50), labradorite (An_50-70), bytownite (An_70-90) and anorthite (An_90-100).</span></p> </div> </div> <div class="element"> <h3>Mineral Name</h3> <div class="element-text">plagioclase<br />feldspar</div> </div> felsic igneous mafic metamorphic sedimentary 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/. Description An account of the resource This glossary describes a number of geological terms with which the 1A students should become familiar.<span> It is by no means an exhaustive list, but is aimed to help you understand the material within the first year course.</span> Title A name given to the resource Glossary 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>Platy</h2> Subject The topic of the resource Crystals which are very thin and sheet-like are described as having a platy form. They are thinner than tabular crystals and less elongate than bladed crystals. 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/. Description An account of the resource This glossary describes a number of geological terms with which the 1A students should become familiar.<span> It is by no means an exhaustive list, but is aimed to help you understand the material within the first year course.</span> Title A name given to the resource Glossary 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>Pleochroic halo</h2> Subject The topic of the resource Pleochroic haloes are tiny spheres of dark discolouration within crystal grains. They are attributed to the presence of zircons trapped within crystals of other minerals, such as biotite mica. Zircon (Zr[SiO4]) is a common accessory mineral of many igneous rocks. It often crystallises early, and becomes trapped within grains of later-crystallising phases. Zircons contain a high proportion of radioactive elements. When these decay, they damage the crystal structure of the surrounding grain, producing a pleochroic halo. Description An account of the resource <em>Have a look at the <strong>alkali basalt (<a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/1">L100</a>)</strong> in the 1A Reference Series.</em> 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/. Description An account of the resource This glossary describes a number of geological terms with which the 1A students should become familiar.<span> It is by no means an exhaustive list, but is aimed to help you understand the material within the first year course.</span> Title A name given to the resource Glossary 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>Plutonic</h2> Subject The topic of the resource Plutonic rocks and textures are those associated with deep magmatic intrusions, where cooling is slow. Crystals are thus able to grow very large, producing coarse-grained textures. This term is restricted to large igneous bodies more than hundreds of metres in diameter. 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/. Description An account of the resource This glossary describes a number of geological terms with which the 1A students should become familiar.<span> It is by no means an exhaustive list, but is aimed to help you understand the material within the first year course.</span> Title A name given to the resource Glossary 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>Poikilitic</h2> Subject The topic of the resource An igneous texture in which a small number of large grains enclose many smaller grains of another phase. Description An account of the resource <em>Have a look at the <strong>gabbro (<a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/10">L141</a>)</strong> in the 1A Reference Series.</em> 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/. Description An account of the resource This glossary describes a number of geological terms with which the 1A students should become familiar.<span> It is by no means an exhaustive list, but is aimed to help you understand the material within the first year course.</span> Title A name given to the resource Glossary 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>Polycrystalline</h2> Subject The topic of the resource <p>A crystalline sample of a single mineral, containing many crystals. Quartzite, for example, is polycrystalline quartz.</p> Description An account of the resource <em>Have a look at the <strong>quartzites (<a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/39">L520</a>, <a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/40">L521</a>)</strong> in the 1A Reference Series.</em> 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/. Description An account of the resource This glossary describes a number of geological terms with which the 1A students should become familiar.<span> It is by no means an exhaustive list, but is aimed to help you understand the material within the first year course.</span> Title A name given to the resource Glossary 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>Porosity</h2> Subject The topic of the resource <p>The proportion of the material occupied by space, measured in volume percent. A porous material contains fluid-filled spaces, or pores, while a non-porous material does not. NB, make sure you understand the difference between porosity and permeability.</p> Description An account of the resource <div> <div class="element-set"> <div class="element"> <div class="element-text"> <p><em>Compare with<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/234">permeability</a>.</em></p> </div> </div> </div> </div> <div> <div class="element"> <div class="element-text"></div> <div class="collection"></div> </div> </div>