<p>Nephrite jade from the Precambrian of Wyoming, USA. (cut &amp; polished surface; ~6.6 centimeters across at its widest)
</p><p>Nephrite jade (nephritite) is a crystalline-textured to felted-textured metamorphic rock principally composed of one or more amphibole minerals (tremolite to actinolite, Ca2Mg5Si8O22(OH)2 to Ca2(Mg,Fe)5Si8O22(OH)2).
</p><p>Nephrite jade was discovered in Wyoming in the 1930s, resulting in a "jade rush" that lasted for several decades.  Most recovered material is alluvial jade, produced by paleoerosion of jade outcrops.  Eroded clasts of jade were transported downstream and subsequently buried with other poorly-sorted sediments.  Some Wyoming jade has been collected from in-situ outcrops.
</p><p>This sample is "lode jade" and comes from a "vein" in granite.
</p><p>Age: Precambrian (probably Proterozoic)
</p>
Locality: undisclosed site in the Granite Mountains, Fremont County, Wyoming, USA
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a>
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/jsjgeology/49703436701/">Nephrite jade (Precambrian) (Granite Mountains, Fremont County, Wyoming, USA) 3</a>