Sandra Hughes., age 10, of newport news, va., For her question:

What causes the colors of petrified wood?

Most petrified wood is quartz stone colored with traces of other minerals. Sometimes these impurities are microscopic crystals of color scattered throughout the basic mineral. A trace of nickel oxide gives a bright app1e green color to the petrified wood. Traces of manganese may color the stone pinkish broym or bluish¬violet.

Scme petrified wood is called tigerts eye  perhaps because it glows with an eerie ye11ow fire. The glow may came from fine hairs of asbestos imprisoned in the stone. Most of the other radiant colors of petrifi£d wood are added by small smidgens of iron, nickel or manganese.