1 10 1 https://wserv3.esc.cam.ac.uk/p1acollections/files/original/5e37a66fc246f7e8a088a4e4c0d011bd.jpg 541861a9fa9a4ae459f66f0e9c425bb3 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>Zircon</h2> Description An account of the resource <div class="element-set"> <div class="element"> <div class="element-text"> <h3>Formula</h3> </div> </div> </div> <div class="element-set"> <div class="element"> <div class="element-text">Zr[SiO₄]</div> </div> <div class="element"> <h3>Structure</h3> <div class="element-text"> <p>Orthosilicate</p> </div> </div> <div class="element"> <h3>Crystal System</h3> <div class="element-text"> <p><em>Crystal system:</em><span> </span>tetragonal (+)</p> </div> </div> <div class="element"> <h3>Physical Properties</h3> <div class="element-text"> <p><em>Colour in hand specimen:</em><span> </span>reddish brown, yellow, grey, green or colourless<br /><em>Hardness:</em><span> </span>7.5</p> </div> </div> <div class="element"> <h3>Optical Properties</h3> <div class="element-text"> <p><em>Colour in plane polarised light:</em> colourless to pale brown<span> </span><br /><em>Pleochroism:</em> very weak<br /><em>Relief:</em> high<br /><em>Birefringence:</em> 0.042-0.065; 3rd order green to 4th order green<br /><em>Extinction:</em> straight<br /><em>Twinning:</em> rare</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></p> </div> </div> <div class="element"> <h3>Mineral Name</h3> <div class="element-text">zircon</div> </div> </div> Subject The topic of the resource Zircon is a common accessory mineral of many igneous rocks. Pleochroic haloes are formed by damage to the crystal lattice of enclosing minerals by the radioactive decay of elements such as Th and U in zircon. These may be particularly noticeable in biotite grains in old granitic rocks. granite radiation thorium uranium