A vein or lode is known to exist within the meaning of the mining act when it could be discovered by or is obvious to anyone making a reasonable and fair inspection of the premises for the purpose of making a location of a placer mining claim. This term is not to be taken as synonymous with located vein and refers to a vein or lode whose existence is known as distinguished from one that has been appropriated by location. Hence, a regular location is not necessary before a vein or lode can be a known vein or lode. The time at which a vein or lode must be known to exist to except it from a placer patent is the time at which the application for a patent is made and to contain minerals in such quantity and quality as to justify expenditure for the purpose of extracting them.