Saw this and think that it’ll really be helpful to me.
Ra is a sound object / synthesizer which uses laser for scanning the irregularities of the surface of the pyrite disc and further transforms this data to produce sound. Pyrite disc is a rare form of pyrite which is crystallised in radial shape (as unusual disc spherulites) which also was named ‘pyrite suns’ or ‘pyrite dollars’. The only deposit where pyrites of such morphology are found is in Illinois state (USA). Pyrite suns were formed around 300 million years ago.
more information and images – vtol.cc/filter/works/Ra