Gold nuggets found in rivers & streams (= placer gold) usually have irregular, somewhat rounded shapes.  It's rare to find placer gold having a crystalline structure.  HereŐs the top and bottom of a nice gold crystal from VenezuelaŐs Santa Elena Placer Gold District.


The top of the specimen (left photo) shows the upper half of an octahedral crystal (a square pyramid).  Notice that each of the four faces of the pyramid are embayed.  Such features are not uncommon in natural crystals.  The terms hopper octahedron or skeletal octahedron would be applicable here.  A few grains of sediment are stuck at the bottom of a couple of these cavities (e.g., just visible in the bottom cavity of the left photo).  The right photo shows the underside of the specimen.  It has the typical irregular, dimpled, somewhat rounded shape of many placer gold nuggets.


Geologic context: placer gold in modern alluvial deposit; gold is derived from weathering of conglomeratic paleoplacers in the UairŽn Formation, Roraima Supergroup, upper Paleoproterozoic, ~1.7-1.8 billion years.


Locality: unrecorded locality in the Santa Elena Placer Gold District, near Santa Elena de UairŽn, Grand Savannah River region (La Gran Sabana), southeastern Bolivar State, southwestern Guyana Highlands, southeastern Venezuela.



Crystalline placer gold (skeletal octahedral crystal; hopper octahedral crystal) (5.5 mm across) from the Santa Elena Placer Gold District of Venezuela.




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