10 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>Carlsbad twinning</h2> Subject The topic of the resource <div> <div class="element-set"> <div class="element"> <div class="element-text"> <p></p> </div> </div> </div> </div> <div> <div class="element"> <div class="element-text"></div> <div class="collection"></div> </div> </div> Description An account of the resource <em>See<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/252">simple twins</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>Bladed</h2> <div class="element-set"> <div class="element"></div> <div class="element"></div> <div class="element"> <div class="element-text"></div> </div> </div> Subject The topic of the resource <span>Crystals with a flattened, elongate habit, resembling blades of grass are described as bladed. Bladed crystals are more elongate than platy crystals, and thinner than tabular crystals.</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>Birefringence</h2> Subject The topic of the resource <p>Light passing through a mineral is resolved into two permitted vibration directions. In an anisotropic mineral light travels at different velocities along the two vibration directions. The ray travelling in the slow vibration direction will be retarded compared with the ray travelling in the fast vibration direction. On leaving the mineral grain the two rays will interfere, producing interference colours.</p> <p>When the slow ray exits the mineral grain the fast ray will already have exited the grain and travelled an additional distance know as the optical path difference, or retardation (Δ). This distance is proportional to the thickness of the mineral grain (t) and the difference in the refractive indices of the two vibration directions (n₁-n₂):</p> <p>Δ = t(n₁-n₂)</p> <p>The birefringence is the difference in the refractive indices of the two vibration directions (n₁-n₂).</p> <p>When rotated under cross-polarised light anisotropic minerals display changing interference colours called birefringencecolours. The birefringence (n₁-n₂) of the mineral can be determined from these colours using a Michel-Levy chart.</p> 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>Argillaceous</h2> Subject The topic of the resource <p>Rocks comprising, or containing a significant proportion of, clay are described as argillaceous.</p> Description An account of the resource <div> <div class="element-set"> <div class="element"> <div class="element-text"> <p><em>Have a look at the<strong> argillaceous limestone (<a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/29">L350</a>)</strong> in the 1A Reference Series.</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>Aphanitic (or aphyric)</h2> Subject The topic of the resource <span>Igneous rocks made up of grains too small to be seen with the naked eye have an aphanitic texture. These rocks do not contain phenocrysts. They are non-porphyritic.</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>Anisotropic</h2> Subject The topic of the resource <div> <div class="element-set"> <div class="element"> <div class="element-text"> <p>The speed of light through any medium is inversely proportional to the refractive index of the medium. The refractive index of a mineral is determined by the arrangement and type of atoms within its structure.</p> <p>If the structure of the mineral allows light to travel at different velocities depending on the direction in which the light is passing through it, the mineral is anisotropic. That is to say, it has different refractive indices in different orientations.</p> </div> </div> </div> </div> Description An account of the resource <em>Compare with<span> </span><a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/213">isotropic</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>Anhedral</h2> Subject The topic of the resource <span>A crystal displaying none of its characteristic crystal faces is called anhedral.</span> Description An account of the resource <em>Have a look at the <strong>granodiorite (<a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/8">L120</a>)</strong> for anhedral quartz, biotite and plagioclase.</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>Amygdale</h2> Subject The topic of the resource <span>A vesicle (necessarily in an igneous rock), which has been filled in by a mineral crystallising from late-stage fluids. Amygdales are commonly produced by the crystallisation of <a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/57">quartz</a>, <a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/64">calcite</a> or zeolite.</span> Description An account of the resource <em>Have a look at the <strong>amygdaloidal basalt (<a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/11">L161</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>Amorphous</h2> Subject The topic of the resource <span>Amorphous materials are non-crystalline solids. That is to say that they do not display long-range order in their structures. Glass is amorphous.</span> Description An account of the resource <em>Have a look at the<span><strong> rhyolite glass (<a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/7">L113</a>)</strong> i</span>n 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>Alteration</h2> Subject The topic of the resource <span>Rocks undergo mineralogical change at low pressures, produced by reactions with circulating fluids. The replacement of the original minerals in the rock tends to take place primarily along cracks and around the edges of grains, though whole mineral grains can be replaced. The decomposition of olivine to serpentine is a common example of alteration.<br /></span> Description An account of the resource <em>Common alteration minerals include clays for plagioclase, <a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/54">serpentine</a> for olivine, and <a href="https://wserv3.esc.cam.ac.uk/p1acollections/items/show/53">chlorite</a> for ferromagnesian minerals such as biotite.</em>