The Spiral Limestone Column is a beige-white building-block with diagonal grey stipes on four sides and a grey grid pattern on two sides. It can be crafted in your Crafting Menu (default key "Q") or at Crafting Tables (that still exist in worlds created before R22 on September 16th 2015), but only after the crafting-recipe has been unlocked upon taking/crafting a Straight Limestone Column for the first time (unlocked by mining Limestone from the Fossil layer underground with at least a Stone Mining Cell). To craft 8 (blocks of) Spiral Limestone Columns, you'll need (as of R29 in February 2016):