<p>Nephrite jade with quartz crystals from the Precambrian of Wyoming, USA. (public display, National Rockhound Hall of Fame, Murdo, South Dakota, USA)
</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>The dark green to black nephrite jade shown above has some inclusions of whitish-colored, hexagonal quartz crystals.  
</p><p>Age: Precambrian (probably Proterozoic)
</p>
Locality: unrecorded/undisclosed locality in 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/24393804579/">Nephrite jade with quartz crystals (Precambrian; Wyoming, USA) 1</a>