Re: where does BLACK sand come from?

Black sand

Sand is defined as grains that are between approximately 0.001m to 0.0001m.
The grains themselves are typically derived from the nearby bedrock. Wave 
action breaking down the rock and crushing it untill it remembles sand.  
Hawaii is especially known for its black sand beaches.  This is beacuse all 
of the islands are composed of basalt (cooled lava). Basalt, because of its 
composing minerals, is a black rock, therefor.....black sand beach.