The matrix on which these lovely green calcite crystals formed resembles the tree bark that it once was, before being buried in the Earth by later sediments and fossilised into quartz when silica rich waters permeated through the rocks and precipitated their load, replacing the wood. The calcite was precipitated later, from carbonate rich waters. The crystals get their green colour from Vanadium, which also contributes to the colour of some emeralds, particularly African stones. I sadly don’t have a scale for the piece, but it was found in Utah.
Petrified Chromium Colored Wood Limb (Araucarioxylon arizonicum) - From a locality near Winslow, Navajo County, Arizona
From one of the oddest finds of Petrified wood in the world, this Conifer tree existed between 65 and 200 million years ago during the Triassic Era. When the tree died and was becoming petrified, it became exposed to the mineral Chromium (same mineral which colors Emeralds). Native Americans were the first to find the material and used it in jewelry making but kept the location a secret until it was eventually rediscovered and authenticated by the Smithsonian. These specimens are natural hygrometers. When dry they become a very light pale green and when wet or exposed to humidity they turn a deep green.