The crystals of Jamesonite are acicular (needle-like), which is its distinctive feature. Normally they are not as big as Stibnite and perhaps more brittle. The difference between Jamesonite and Galena is by Jamesonite’s darker gray color. At one glance, Boulangerite is mistaken for Jamesonite, which is known for its flexible crystals. Also the sulphide, Millerite, has somewhat same acicular crystals; however, you can easily make it out by its yellow color.
The occurrence of Jamesonite is through hydrothermal fluids, mostly in veins along with the other antimony sulfides and also silver, lead or even copper, rich in antimony sulfides. Cornwell in England, where it was originally found in 1825 is a fine illustration of an occurrence like this.
The other places where Jamesonite was obtained are Arkansas, Southern Dakota, USA; Mexico, Zacatecas and Rumania. Jamesonite is not a mineral that occurs commonly.
Jamesonite represents one of the rare minerals of sulfide found in the form of delicate acicular crystals, with the appearance of fibers in the form of hairs that are thick enough to envelope the crystal with their fibrous hairs. If not, it becomes sparingly dispersed among other minerals and mistaken for the real hairs.
Derivation of Name
Jamesonite was named after Robert Jameson a mineralogist of Scotland who was the first person to discover this mineral.
Color - Steel gray, lead gray and deep lead gray
Luster – Metallic
Fracture –It is brittle and normally found with the non-metallic minerals and with glasses
Transparency - Opaque
The minerals connected with Jamesonite are: Arsenopyrite, Sphalerite, Pyrite and Galena Stibnite.
2.5 on the Mohs Scale
5.5 - 5.63, Approximately = 5.56