What is the difference between a carnelian and a red agate?

Carnelian is a reddish brown crystal cleansing which belongs to the silica mineral Chalcedony family. It's reddish brown color is derived from its iron-oxide impurities. It is naturally found Brazil, India and Germany. read more

Agate and carnelian are the same species: Chalcedony. If a chalcedony have bands then it included in the Agate variety. Carnelian is the red or orangy variety of chalcedony that dont have band. Generally if it is banded even if is red, it will included into agate variety (although some people might have different standard). read more

Some can have started as red-orange agate and have had the obvious banding cut away (or oriented so that it is not visible). In many cases, it is a distinction without a difference, as both are red-orange cryptocrystaline quartz. read more

Actually, red agate is carnelian and is chalcedony, and is chrysoprase, and is agate, and is plasma and is sard (though sard is normaly thought of as being more opaque and more less orange). read more