<a href="https://en.wikipedia.org/wiki/Calcite" class="extiw" title="en:Calcite">Calcite</a> containing <a href="https://en.wikipedia.org/wiki/Niobium" class="extiw" title="en:Niobium">Niobium</a> (giving it distinctive bluish color), from Medford Quarry, Caroll County, Maryland.  Collected 2002.  Scale bar is 1 cm.
<a href="https://en.wikipedia.org/wiki/User:Jstuby" class="extiw" title="en:User:Jstuby">Jstuby</a> at <a class="external text" href="https://en.wikipedia.org">en.wikipedia</a>
6 February 2010 (original upload date)
<span class="int-own-work" lang="en">Own work</span><br>Transferred from <a class="external text" href="https://en.wikipedia.org">en.wikipedia</a>