Octahedron faces are composed of numerous microscopic cube corners. Trapezoidal icositetrahedron faces are also rough, composed of numerous tiny cube terminations. Dodecahedron and cube faces are smooth and have high lustre. Very small crystal faces record the presence of another crystal form, perhaps the hexoctahedron or trisoctahedron. The crystal is transparent and nearly flawless internally, though curved wires of a probable sulphosalt and an air bubble are visible.
Published (Figure 15) in The Mineralogical Record, volume 52, March-April 2021. Smith & Holtkamp, Twinning in Fluorite Crystals.