<p>Hydrothermal quartz-gold vein sample (3.2 cm across) from the Harvard Open Pit Mine, northwestern side of Rt. 49/Rt. 108, western side of Woods Creek, just west of Jamestown, western Tuolumne County, Sierra Nevada foothills, central California, USA (37° 56’ 50” North , 120° 36’ 20” West).
</p><p>Geology - hydrothermal quartz-gold veins of the Mother Lode Gold Belt occur in the Melones Fault Zone (= boundary between the Foothills Terrane and the Don Pedro Terrane).  To the east of the fault zone is Jurassic slates.  To the west of the fault zone is serpentinite melange.
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Age - The Melones Fault Zone was active principally in the Late Jurassic and Early Cretaceous.  Gold-quartz mineralization occurred during the late Early Cretaceous, at about 108 to 127 Ma.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a>
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<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/jsjgeology/14532992888/">Hydrothermal quartz-gold vein (Mother Lode Gold Ore, California) 1</a>