A more thorough explanation:

A discovery vein is a continuous body of mineral or mineralized rock that fills a seam or fissure in the earth's crust. It is within defined boundaries that clearly separate it from surrounding rock. This term is commonly used in mining law.

The discovery vein is the primary vein used for locating a mining claim. This means that if a miner discovers a vein of valuable minerals, they can claim the area around that vein as their own and begin mining operations.

For example, if a miner discovers a vein of gold in a particular area, they can stake a claim to that area and begin extracting the gold from the vein. The discovery vein is the key to their claim and the source of their profits.