Many minerals have no cleavage, and so break in an irregular pattern. Other minerals will fracture in a conchoidal pattern, similar to when glass fractures. Different minerals have different densities, and therefore weigh differently. This fact is known to anybody who has ever tried to pan for gold. Gold , being 'heavier' than the other rocks and minerals, sinks when in water, making it easy to collect.
Geologists measure the ratio of the mass of a mineral to a mass of an equal volume of water.
This is the minerals specific gravity . Water has a specific gravity of 1. Heavier' minerals like gold and galena have a higher specific gravity than 'lighter' minerals like quartz. Finally, many minerals have unique or special properties that make their identification easy. Halite has a salty taste while few other minerals have any taste at all.