Boltwoodite is a rare potassium sodium uranyl silicate. This fine specimen features a well-placed, 3.8 cm vug highlighted with radial clusters of super-bright, lemon-yellow boltwoodite needles. The vug is lined with smoky-brown calcite scalenohedrons and the boltwoodite clusters surround a 1.7 cm, lustrous, colorless calcite scalenohedron. Ex. Rob Smith Collection.