Short answers, pulled from the story.
Geotechnical engineers distinguish clay particles as smaller than 2 micrometers according to ISO 14688 standards. This definition separates clay from other soil types based on specific dimensional criteria.
Some of the earliest pottery shards recovered date to around 14,000 BCE in central Honshu Japan. These fragments belong to the Jōmon culture and represent humanity's first major engagement with fired earth.
Firing to the earthenware stage removes additional water causing irreversible covalent bonding. This process transforms kaolinite into non-clay metakaolin which remains rigid if re-moistened.
Quick clay indigenous to Norway North America Northern Ireland and Sweden causes deadly landslides. These sensitive clays prone to liquefaction break foundations and ruin road beds when they absorb water.
Between one-half and two-thirds of world population live or work in buildings made with baked clay bricks. Clay serves as a defining ingredient in construction materials that provide structural integrity globally.