The hopper crystals form due to the disparity of growth rates between the crystal edges and the crystal faces. Color is silver white often with a multi-colored iridescent tarnish. Luster is metallic. Crystals are opaque. Laboratory grown crystals display trigonal hopper crystals that appear pseudocubic.
Fracture is uneven or jagged.
Streak is silver to white. Associated Minerals include bismuthinite and ores of cobalt and silver found in hydrothermal veins such as cobaltite and acanthite . Best Field Indicators are tarnish, density and cleavage. Hopper crystals in laboratory specimens are unmistakable.