looking at the malachite on page 2 i was reminded of something i heard a long time ago

this info may be wrong as i didnt search it to confirm before posting but seems correct

in old paintings they used azurite to color things blue - the sky for example

over time the azurite changes to malachite

so often old paintings have green skies due to decomposition of azurite into malachite

just found that interesting and felt like adding it