Sunday, July 29, 2018

If you put chalk under a powerful microscope—white cliffs of Dover type chalk, not the modern blackboard variety—you will see something like this Because it’s not just a rock. It’s an accumulation of ancient skeletons: the armored husks of...

 If you put chalk under a powerful microscope—white cliffs of Dover type chalk, not the modern blackboard variety—you will see something like this Because it’s not just a rock. It’s an accumulation of ancient skeletons: the armored husks of single-celled, ocean-dwelling plankton. Via here.

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