The Bible doesn't mention what type of tree was used to make the cross on which Jesus was crucified, however, Rohault de Fleury, "Memoire sur les instruments de la Passion", Paris, 1870, 63 wrote, "A microscopic examination of the fragments of the Cross scattered through the world in the form of relics reveals the fact that it was made from a pine-tree."

Keep in mind, that there is no proof that the relics believed to be from the cross of Calvary are indeed from the cross upon which Christ Jesus was crucified.