SCANNING ELECTRON MICROSCOPE STUDY OF HIGH VALUE EMERALD AND RED BERYL FROM NORTH AMERICA

Inclusions within crystals are important when determining the crystal’s value. The more inclusions within the crystal can decrease its value. Red beryls from the topaz rhyolite in Utah along with emeralds from the Crabtree pegmatite near Spruce Pine, North Carolina are currently being studied in detail. A potential pegmatite equivalent exists between the Wah Wah Mountain and Thomas Range rhyolites and the Crabtree Mine pegmatite. The red beryl-bearing rhyolite is exposed on the surface compared to the deep emplacement of the emerald-bearing pegmatite of the Crabtree Mine. The two rhyolites from Utah could possibly be an eruptive pegmatite magma similar to that of the rhyolite of Honeycomb Hills, Utah (Congdon and Nash, 1991). Inclusions can also give insight into the cooling history of the rock and have been studied in detail with the Scanning Electron Microscope (SEM). Many inclusions were found along fractures within the emeralds. Some were located along the rim while others were randomly oriented throughout the crystals. Various inclusions grade in size from rim to core while other emeralds have quartz overgrowths. The majority of the inclusions are quartz but zircon, biotite, minor muscovite, potassium feldspar, pyrite, and apatite are also found within the crystals. The next step of our research will include continuing SEM analysis of detailed inclusions throughout the emerald and red beryl. Some of the red beryl have decreasing inclusions from center to rim. Zoning will also be studied in more depth through a core to rim traverse of the crystals. Other minerals within the pegmatite will also be studied in order to look at inclusions and their correlation to the cooling history.