AL-BIRUNI (973-1050)

The Persian scholar al-Biruni lived around the same time as ibn-Sina. He pioneered the idea that light travels faster than sound, promoted the idea that the Earth rotates on its axis and measured the density of 18 precious stones and metals.

portrait of al-biruni

He classified gems according to the properties: colour; powder colour; dispersion (whether white light splits up into the colours of the rainbow when it goes through the gem); hardness; crystal shape; density.
He used crystal shape to help him decide whether a gemstone was quartz or diamond.

He noted that flowers have 3,4,5 or 8 petals, but never 7 or 9.

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