24 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>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>. 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 Pleochroism Subject The topic of the resource Some minerals are pleochroic. When rotated under plane polarised light they change colour. Biotite and the amphibole hornblende are pleochroic. Description An account of the resource <em>Have a look at <strong><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/50">hornblende amphibole</a> (M201, M211) </strong>and <strong><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/52">biotite mica</a> (M303, M304)</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> 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>Porphyritic</h2> Subject The topic of the resource <div> <div class="element-set"> <div class="element"> <div class="element-text"> <p>An igneous rock containing phenocrysts in a fine-grained groundmass is said to have a porphyritic texture.</p> </div> </div> </div> </div> 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>Porphyroblast</h2> Subject The topic of the resource <p>A porphyroblast is the metamorphic equivalent of a phenocryst. Do not confuse them! It is a large crystal set into a finer-grained fabric, in a metamorphic rock.</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/236">phenocryst</a>.</em></p> </div> </div> </div> </div>