Agate is a kind of quartz and it is a mineral . Agate can come in many different kinds and colors . Other forms of agate include Lake Superior agate , carnelian agate ( usually exhibiting reddish hues ) , Botswana agate , Ellensburg blue agate , blue lace agate , plume agates , tube agate ( with visible flow channels ) , fortification agate ( which exhibit little or no layered structure ) , fire agate ( which seems to glow internally like an opal ) and Mexican crazy-lace agate ( which exhibits an often brightly colored , complex banded pattern ) also called Rodeo Agate and Rosetta Stone depending on who owned the mine at the time .