How to Find and Harvest Ice with Trapped Items
Where to Look
Rare Ice generates naturally in cold biomes — think snowy plains, ice spikes, frozen oceans, snowy taiga, and the frozen peaks of mountains. The trapped-item ice looks identical to normal ice at a glance, so you need to scan carefully. Walk along the surface of frozen lakes and rivers, check the edges of glaciers, and look at ice exposed in cave ceilings or cliff faces in snowy regions. Ice that contains an item will often show a faint silhouette of the item inside the block, so look for shapes that break up the usual blue transparency.
Breaking It Safely
Do not use a Silk Touch pickaxe unless you want the ice block itself — you want the item. Break the ice with any pickaxe (or even by hand, though it takes longer) so the block shatters and drops its contents. If you break it with a normal tool, the ice disappears and the trapped item pops out as a collectible drop. Bring a shovel or pickaxe with decent efficiency, plus a torch or Night Vision potion if you are searching under ice shelves or in caves. A bucket of water is handy if you accidentally break ice over a drop.
Maximizing Your Haul
Frozen oceans are the richest source because ice stretches for hundreds of blocks. Sweep in straight lines and mark where you have been. Combine this with a boat so you can glide across the surface quickly while scanning for silhouettes.