These are "Conchas" Chalcedony agate rosette, composited of fine tine drusy quartz crystals. Specimen are either or both Lime green or purple fluorescence under U.V. light.Approx. 1-1/2" across. Specimen is dark gray with some brown and a white center. lightweight at 15.8 grams. Good for wire wrapping as pendent. Rio Grande do Sul, Brazil.