The river-worn agates were mined in India in 1960s and 1970s in large quantities for cabbing purposes and I still see them in old rough collections. They're identified by their smooth river-worn appearances usually black skinned or yellow skinned (likely to be from a different location). It's kinda surprising that very little in way of colorful agates have been found in the Deccan Trap basalt areas but then again, different environmental factors, the kind that produced an abundance of zeolite minerals and other associated minerals. The colors are generally dull gray to black sometimes with yellow colors. There are some attractive and chaotic distribution of colors in some agates. Some agates are still being mined today as in case of those in the Masharashtra region.