This ruby sapphire mixed crystal is from the Propst farm in Lincoln County, North Carolina, USA. This location contains volcanic and alluvial deposits that contain ruby, and sapphire crystals. They are varieties of the mineral corundum which is an oxide that contains the elements Al and O. In pure form corundum is colorless but trace impurities in the crystal lattice can color it with a variety of colors. This is double terminated crystal with a hexagonal morphology. It is mostly ruby but it does have zones of blue sapphire. It also has some druse hematite crystals on and penetrating the crystal. This crystal weighs 310 carats and it measures 1 3/4 x 1 5/8 x 1/2 inches or 45 x 41 x 13 mm.