Thin section of ooids in the Keel Formation (Silurian), Oklahoma.  Image was taken with plane polarized light at 50x magnification.  Version with crossed polars is provided below and at <a class="external free" href="https://upload.wikimedia.org/wikipedia/commons/archive/7/79/20130521153026%21Keel_Fm_110113-3_50x_xpl_j.tif">http://upload.wikimedia.org/wikipedia/commons/archive/7/79/20130521153026%21Keel_Fm_110113-3_50x_xpl_j.tif</a>.  Thin section was prepared with blue epoxy and alizarin red stain for calcite
<a href="//commons.wikimedia.org/wiki/User:Rygel,_M.C." title="User:Rygel, M.C.">Michael C. Rygel</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>