In Survival mode, iron, gold, and diamond ore generate in specific patterns (veins). Experienced players don't need X-Ray. They know:

Many players use "exclusive" texture packs to make common blocks (like dirt or stone) transparent, revealing ores and chests. :

Most free or cheap "X-ray Exclusive" tools are simply or Chrome extensions that claim to hook into the game’s WebGLRenderingContext .

If you don't want to use a texture pack, players have discovered "vanilla" glitches that offer a temporary X-ray view: