The George W. Lund Memorial Petrified Forest (formerly known as Leadville Petrified Forest) is located north of the Black Rock Desert, Nevada.  A 40 acre reserve set aside by BLM has about 250 located petrified wood stumps that are likely giant sequoia, made mostly from agate & opal.  They are of Miocene age (15-16 million years ago).  Walk around the area to locate stumps still standing upright with some of them up to five feet in diameter, many of them having noticeable tree rings.  Sadly this area was part of a much larger petrified forest; years of rock collecting & blasting for mining & exploitation had greatly changed what the site used to look like.