The Mohs Hardness Test
Hardness is one of the most reliable field tests. Talc scratches with a fingernail (1), quartz scratches glass (7), and a steel knife sits at ~5.5. Carry a nail, a piece of glass, and a quartz crystal as reference points and you can narrow down most unknowns in seconds.
Luster: How Light Bounces Off
Metallic luster (like pyrite or galena) vs. vitreous/glassy luster (quartz, glass) vs. silky or pearly luster (selenite, talc). This single observation eliminates huge categories of minerals before you do anything else.
Crystal Structure and Habit
Quartz grows in 6-sided prisms with pointed terminations. Calcite forms rhombohedra and has perfect cleavage in 3 directions. Cubic crystals (halite, galena, fluorite) are dead giveaways. Learning the 6 crystal systems helps you predict what a mineral will look like even when it's not well-formed.
The Streak Test
Drag the mineral across unglazed porcelain tile (a streak plate). The color of the powder is often different from the specimen — pyrite looks gold but leaves a greenish-black streak, hematite leaves a red streak no matter what color the specimen is.
Use AI Rock Identification
Can't figure it out in the field? Take a photo with the We Lick Rocks "Name That Rock" AI tool. It analyzes color, crystal habit, texture, and luster to suggest the most likely identification — and gives you collector tips specific to that mineral.