Niccolite and sphalerite. Settlingstones Mine, North Pennines, Britain
250µm
Niccolite showing the typical radiating habit (centre), known as an 'ice flower' texture. The strong anisotropy of niccolite is well seen. Sphalerite (grey, bottom centre) shows light-colored internal reflections.
Polished block, plane polarized light, x 80, air
