New Mexico Mineral Symposium — Abstracts

"Herkimer-style" quartz occurs in the Cretaceous Mesaverde Group in the Jornada del Muerto Basin, Sierra County, New Mexico. Quartz crystals up to four inches occur with calcite as fracture or fault fillings within sandstone and limestone units. Crystals on matrix grow on surfaces displaying near vertical slickenlines. Free, double-terminated crystals are suspended in calcite. Many low-temperature macroscopic inclusions of gas, liquid, petroleum, anthraxolite, and carbonate occur in various combinations within crystals. Crystals fluoresce blue, red, and orange under both longwave and shortwave UV light. The strike of the quartz-filled fractures varies between 205 and 260° with near vertical dips. Normal, rift-related faulting is dominant in the area. Basaltic dikes are common locally and are concordant with faults.