Petrified palm wood is the state stone of Texas and the state fossil of Louisiana.  It comes from palm trees in the Oligocene Epoch, between 20 - 40 million years ago, give or take a few years.  

The characteristic spotted look of palmwood is from the rod like structures within the grain of the wood. Depending upon the angle the lapidary uses to cut the stone, these structures show up as spots, tapering rods, or lines.

Petrified palm wood is a variety of chalcedony and is very hard, around 7 1/2 on the Mohs scale of hardness and takes a wonderful polish which makes it a great stone for jewelry.