What Is It?
A fossil tree. This particular fossil was formed when it fell into the mud and sediment at the bottom of a prehistoric  lake and was buried.  Over time minerals in the water that had soaked into the logs replaced the once living tissue. This process, called silicification, provided a perfect replica of the once living tree.

Why All the Colors?
Petrified WoodThe mineral water that soaks into the wood is full of elements like  manganese, iron and copper.  These impurities give petrified wood a variety of colors. Pure quartz crystals are clear, but when contaminants are added to the process the crystals take on a veritable plethora of  tints.  Here is a list of elements and the colors they are likely to produce.

Carbon - black
Cobalt - green/blue
Chromium - green/blue
Copper - green/blue
Manganese - pink/orange
Iron oxides - red, brown, and yellow
Manganese oxides - black/yellow

Where Did It Live?
During the Late Triassic, about 225 million years ago, northeastern Arizona was on vacation, located near the equator. This region was near the southwestern edge of the earth’s largest existing landmass, called Pangaea.  An artists rendering is pictured to the right. 
    The tropical location resulted in a climate and environment very different from today where the landscape is pine trees and sagebrush. The land was flatter, there were tons of huge trees, bushes and plants and the vegetation was thick and lush.  A lot like East Texas and Louisiana is today.  Hot, sticky, tons of bugs, and lip smackin’  BBQ.
    About this time, the super-continent began to break apart into the modern continents and they eventually migrated to their present locations. Fossil evidence of this ancient land lies in the sediments called the Chinle Formation which are now vividly on display in Petrified Forest National Park.

Vascular  Facts
If you look carefully at a cross section of the specimen you may be able to see the growth rings.  They appear as uniform radial lines. To determine the exact name of a species of tree, scientists cut a cross section of the specimen and examine the cell structure. This specimen is probably an evergreen, possibly an ancient sequoia that lived in the richly diverse, warm forests of the Triassic Period.  At least that is the way that we are going to classify it, taxonomically.

Taxonomy, Please.
Assuming you do have a giant sequoia, here is the family tree, no pun intended.

    Kingdom: Plantae
        Division: Pinophyta
            Class: Pinopsida
                Order: Pinales
                    Family: Cupressaceae
                       Genus: Sequoiadendron
                           Species: gigantium

Field Trip
The most obvious location we would point you towards would be the Petrified Wood National Park in Arizona.  However, every state in the western United States has numerous collecting locations and regional parks of interest to fossil hunters and collectors. Check locally at rock shops and universities.

Petrified Wood NPS