So, I'm confused about agate and carnelian. I thought they were related but just different colors. I looked at wikipedia, and learned both are chalcedony. Too little is said about carnelian to reason it out further.

Agates form inside voids in volcanic masses.

http://en.wikipedia.org/wiki/Agate

http://en.wikipedia.org/wiki/Carnelian

This snippet from the agate article:
Idar-Oberstein was one of the centers which made use of agate on an industrial scale. Where in the beginning locally found agates were used to make all types of objects for the European market, this became a globalized business around the turn of the 20th century: Idar-Oberstein imported large quantities of agate from Brazil, as ship's ballast. Making use of a variety of proprietary chemical processes, they produced colored beads that were sold around the globe.[5]