gems, imitation turquoise, Eilat Stone, feldspar/amphibole-bearing rock

A mottled blue-to-green gem material from Egypt, observed in Cairo and said to be sporadically collected by Bedouin tribespeople, was found to resemble the well-known copper-colored “Eilat stone” of Israel. Two cabochons—a 7.05-ct pear shape and a 3.29-ct oval—were semitranslucent with greenish blue and nearly black dark green areas, the former highly fractured and veined, and the latter containing metallic-luster inclusions. Additional inclusions of saturated greenish blue with lower diaphaneity and some brownish red (likely limonitic) staining were noted. Spot refractive index measured 1.54, and the gems appeared green through the Chelsea filter. The translucent zones fluoresced faint yellowish green under long-wave UV, while the material was inert to short-wave UV. Specific gravity values were 2.67 and 2.74. As standard tests were inconclusive, X-ray powder diffraction revealed the greenish blue areas to be feldspar and the dark green areas amphibole, though species were not identified. EDXRF analysis detected Al, Si, K, Ca, Ba, Mn, Fe, and Cu, with copper likely responsible for the blue coloration. The stones were thus identified as rocks composed of feldspar and amphibole, with other minor mineral components.