Porphyry

por'-fi-ri (in Es 1:6, the Revised Version margin has "porphyry" (the King James Version margin "porphyre") for bahaT, English Versions of the Bible "red (marble)"; the Septuagint has smaragdtes, which was a green stone): Porphyry is an igneous rock containing distinct crystals of feldspar in a feldspathic matrix. It may be purple or of other colors, as green. "Porphyry" is from porphureos, "purple."

⇒See also the McClintock and Strong Biblical Cyclopedia.