Mineral
Jamesonita
Pb₄FeSb₆S₁₄ · Sulfosales
Jamesonite is a lead–iron–antimony sulfosalt.
Classically known as "Feather Ore" for its unmistakable habit. It forms extremely fine, flexible acicular crystals with a hair-like or felt-like aspect. Needles may occur isolated or as small "hedgehog" aggregates. In Peruvian specimens these growths sit on white baryte or quartz matrix.
Etymology
Named in honour of Robert Jameson, an influential (and somewhat obstinate) Scottish mineralogist who was a professor at the University of Edinburgh and had a very famous student: Charles Darwin. The relationship was disastrous. Darwin wrote in his autobiography that Jameson's lectures were so "incredibly boring" that they made him hate geology for years. Jameson was old-school—he believed all rocks formed in water ("Neptunism")—and refused to accept the new volcanic theories.