Opal mineshaft

Opal mineshafts would be a new type of mine shaft that generates on the surface. They could have a straight vertical holes or have a staircase 20 blocks beneath the ground. This would lead to an Opal vein. Opal veins would be a semi rare generation of opal gemstones. Opal mine shafts would have a chance to spawn connected to one of these veins. Opal would be a rainbow\chromatic colored block. A secondary opal block would generate in lower quantities with this opal. As a placeholder name we can call this Galaxy Opal, after its texture resembling a galaxy. Opal would be a purely decorative block.