Chalcedony and Quartz

Chalcedony noun - A milky or greyish translucent to transparent quartz.

Quartz and chalcedony are semantically related. In some cases you can use "Quartz" instead a noun "Chalcedony".

Quartz noun - A hard glossy mineral consisting of silicon dioxide in crystal form; present in most rocks (especially sandstone and granite); yellow sand is quartz with iron oxide impurities.

Chalcedony and quartz are semantically related. Sometimes you can replace term "Chalcedony" with "Quartz", this nouns are similar.