36 cm diam: coal, glass.
When children see this and are asked what it is, they often say it is the stuff used to light the barbecue.
That is not right. For the barbecue charcoal is used, which is wood that has been pre-burned to get rid of water and other organic stuff that would prevent it from burning well. That wood, however, is from a tree that has been cut recently and was maybe 50 years old. Charcoal is only about 50 years old.
The coal shown here is also wood, but of trees that grew 300 million years ago. These trees were destroyed by a natural cataclysm, were covered by the sea, ended up under layers of sediments where they became compressed and transformed into coal.
The coal shown is without doubt the oldest thing in the Museum: 300 million years old ...
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