Framboids

Framboids may be the most astonishing and abundant natural features you've never heard of. These microscopic spherules of golden pyrite consist of thousands of even smaller microcrystals, often arranged in stunning geometric arrays. They are rarely more than twenty micrometers across, and often look like miniscule raspberries under the microscope. The formation of a framboid is the result of self-assembly of pyrite micro- and nano-crystals under the influence of surface forces. They can be...