However, millerite is yellow and boulangerite has flexible crystals. Jamesonite also forms larger prismatic crystals that can be confused with stibnite . Jamesonite crystals have less definition in its crystals and are more brittle. Jamesonite is a sulfosalt, a segment of sulfides where the antimony acts more like a metal than a non-metal and occupies a position where it is bonded to sulfurs. Jamesonite has been called feather ore and grey antimony.
Color is dark gray.
Luster is metallic and silky. Transparency Crystals are opaque. Also in fiberous masses. Cleavage is good in one direction perpedicular to its length. Fracture is uneven.