Gems Notes and Extracts Augusto Castellani, Mrs. John Brogden 1871

PETRIFIED WOOD. ]39LYI.PETRIFIEDWOOD.UNDER this denomination are included, without distinction,all woods that have .undergone such alterationsas entitle them to be numbered amongst minerals.Here, omitting every other kind, we must give ourattention solely to the agate-wood, which most resemblesfine stones.The petrifaction of wood is a wonderful phenomenon.Trunks, branches and roots, which once had life,become mixed substances ; remaining for ages buriedin the earth, and preserved by the infiltration theyexperience, they at last acquire a great degree of hardness: the organic fibres of the once vegetating bodybecoming recipients of silicious saline materials.For the petrifaction of wood, it is necessary1st. That it be of a nature to be preserved underground.2nd. That it remain there covered from air andrunning water.3rd. That it be preserved from the action of corrosives.4th. That it be in a place where there is also a concentrationof liquids containing either metallic particlesor stony molecules loosened, which, without destroyingthe ligneous body, penetrate it and become assimilatedto it, at the same time that its particles dissipate byslow evaporation.