Plural of agate; banded or striped varieties of chalcedony, a semi-precious stone, often with colorful layers.
From Greek 'akhatēs,' possibly named after the Achates River in Sicily where these stones were found. The word traveled through Latin into English.
Collectors go wild for agates because each one is unique—formed over millennia in volcanic rocks, each stone tells a geological story in its bands, and you can find them on beaches worldwide for free.
Complete word intelligence in one call. Free tier — 50 lookups/day.