Leather Library
Not a hide at all, but a dense membrane from the horse's hindquarters — and the most expensive leather on this list by far.
Shell cordovan isn't really a hide in the usual sense — it's a dense, fibrous flat muscle membrane found beneath the skin at a horse's rump, and only two small pieces, roughly 1 to 2 square feet each, can be harvested per animal. That scarcity alone explains a lot of the price. The shell is vegetable tanned over 6 to 12 months — soaked in water, lime, and other chemicals, split into layers, then repeatedly treated with oak-bark mixtures and buffed to its signature glossy finish. The result resists creasing almost entirely, forming smooth "rolls" instead of sharp creases, and develops a rich patina with wear and handling. It's also famously close to waterproof.
More associated with fine dress shoes than Western boots, but it does turn up occasionally on boutique and dress-leaning cowboy boots where a maker wants to showcase something genuinely rare. Raw shell cordovan runs $100–$150 per square foot before it's even made into anything, and finished footwear using it commonly runs into four figures.
Shell cordovan has its own dedicated care products — wipe regularly with a soft, dry cloth, and use cleaners and conditioners made specifically for cordovan rather than general leather products. Store it cool and dry, away from direct sunlight and humidity.