New Mexico Mineral Symposium — Abstracts

West Texas and southern New Mexico are not known for the presence of gem stones, thus this comes as a surprise when we tabulate the gem minerals found in the Franklin Mountains. Given the gemstones of each month, nearly one half the year is present. As yet, no gemstones have been faceted from Franklin Mountain minerals because they lack quality, but their presence provides a tantalizing feeling that there is more yet to be discovered.

Topaz was the first gem mineral reported from the Franklin, and it was discovered as an accessory mineral in the tin pegmatites mined between 1908 and 1911. Photomicro-graphs of topaz are included in the published literature of that time.

Garnet has been reported from several localities in the Precambrian rocks on the eastern side of the range, particularly in the Castner Formation. These are visible in roadcut #3 ascending from the east, and assume large dimensions in the valley past roadcut #1, up to 5 inches on a crystal face. Hitt Canyon also has garnets. The colors are brown, and the mineral forms as a result of contact metamorphism.

Blue beryl is present in pegmatitic rock from Fusselman Canyon, but the only known specimens are in the UTEP Centennial Museum and Department of Geological Sciences collections, and the exact site has been lost. Host material is grey quartz, but aplite dikes in the area are the suspected producers. The sky-blue color makes the material very attractive, and with increased size and transparency the crystals would present an outstanding gemstone. An El Paso 'old timer' maintains that the discovery site is underneath Trans Mountain Road, a distinct possibility.

Zircon crystals up to 1 inch on an edge have been found in the riebeckite dike in the Precambrian rocks. The dike can be seen in roadcut #1 east, but the large zircon crystals are found about 1 mile away to the northwest. The crystals are lustrous and dark red brown and make attractive specimens.

Finally, many fine agates, generally carnelian, banded, and common grey varieties, have been found on the fluvial slopes away from the Franklin Mountains. These agates were actually borrowed from New Mexico by the Rio Grande in eons past.

Other than the latter material, the gem minerals of the Franklin Mountains originated from Precambrian magmatic processes, approximately 1.1 billion years ago. These magmas were of the A or anorogenic type, and the concentration of rare metals, such as Be, Sn, and Zr, and of the halogen F to make topaz, is not unusual.

In the future will there be a Franklin Mountains gemstone district? No. The area is protected in the Franklin Mountain Wilderness Park of the State of Texas, the aggressive and pistol-packin' caretaker lives in Canutillo, Texas, nearby, and collecting is prohibited.