You must have GRIMSTONE and YELLOW BLOCK to make DARK YELLOW BLOCK. This item belongs to color blocks category. DARK YELLOW BLOCK is good to plant before you head to some parkours. Received experience is a mystery. Keep an eye out for the exp counter. Hitting it will break it but you need to count the hits yourself. Seed mathematics is very complicated, but you should get at least 1 seed back from splicing DARK YELLOW BLOCK. Will you strike it rich? You just have to count the gems yourself. Massproducing DARK YELLOW BLOCK can be tricky. You will find out after you have harvested a few.