Rocks and minerals undergo interesting transformations over time. In particular, one of the minerals, which has a relatively high hardness of 6 on the Mohs scale, turns into a common secondary mineral with a hardness of 2. Over time, as a result of weathering, it turns into one of the most common soft rocks in the world. But the transformation does not end there: humanity (in particular, on the territory of Ukraine) even in ancient times invented how to make the first solid artificial material from it. What kind of minerals, rock and artificial material are these?