4 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 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>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>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>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>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>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>Pearly [lustre]</h2> Subject The topic of the resource <span>Unsurprisingly the quality and intensity of light reflected from minerals displaying “pearly” lustre is reminiscent of pearls. This effect is produced by the reflection of light from many thin, coplanar, transparent sheets within the mineral. Muscovite, for example, has pearly lustre.</span> Description An account of the resource <em>Have a look at the <strong><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/51">muscovite mica</a> (M301, M302)</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>Overgrowth</h2> Subject The topic of the resource The crystallisation of one mineral on the surface of another, producing a rim or part of a rim. 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>Orthosilicate</h2> Subject The topic of the resource <span>Silicate minerals in which the SiO4 tetrahedra do not share oxygen atoms with one another are called orthosilicates, or island silicates. These minerals do not contain bridging oxygen atoms.</span> 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>Ooid</h2> Subject The topic of the resource Sub-spherical sedimentary grains comprising a nucleus surrounded by concentric layers of carbonate precipitate. Ooids form abiogenically. They are sometimes referred to as ooliths. Description An account of the resource <em>Have a look at the <strong>oolitic ironstone (<a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/34">L361</a>) </strong>and the<strong> oolitic limestone (<a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/32">L353</a>)</strong> in the 1A Reference Series.</em>