Rainbow stones are used for a lot of crafting items, while the Shiny Rocks can only be crafted into a few items, yet they are very common to find in explore. They pile up without much use, while Rainbow stones are pretty rare and sought after (for me anyways). My suggestion is to make Rainbow Stones craftable by using Shiny rocks of each color.

For example, crafting 5 Shiny Red Rocks, 5 Shiny Black Rocks, 5 Shiny Green Rocks, 5 Shiny Orange Rocks, 5 Shiny White Rocks and 5 Shiny Teal Rocks together, would make one Rainbow Stones.

That way we have more uses for these rocks. Alternately, it would be nice to have more items to be crafted from Shiny Rocks, other than just the small decors that can be made now.