Why did they turn to rock?
They did not really turn to stone. Silica and minerals in solution were forced into the wood, dissolved it, and replaced the wood cells with their own substance.
How is it polished?
By a process of grinding with carborundum and diamond dust, then rubbed with leather buffer. It approaches the diamond in hardness and an ordinary emery wheel will scarcely mark it.
What is the weight of the petrified wood?
About 200 pounds to the cubic foot. It varies.
Why can’t visitors take specimens away with them?
First: Because it is against the United States Law. After that comes consideration of future visitors to the Petrified Forest National Monument. When one reflects that there are about eighty thousand visitors here annually and that if each visitor took what pleased him, it is an unrefutable fact the best specimens would speedily disappear. A visitor would not be satisfied with one small piece. There would be the home folks to consider; the neighbor that fed the left-at-home cat, and the friend who loaned his kodak for the trip. These would all need souvenirs. It would be difficult to choose among several beautiful pieces and so a compromise would be made by taking all of them.
Courtesy National Park Service