Identification
Updated
Naming what you have, and being honest about how sure you are.
Locality first
The most powerful identification tool is knowing where it came from.
A locality has a known species list. Narrowing from every mineral to the twenty found at that mine does more than any test you can run at home.
Which is another reason the field notebook earns its place: it is an identification aid as well as a provenance record.
The ordinary tests
Habit and form, which for many species is diagnostic on sight.
Color, which is weak alone and useful in combination.
Lustre and transparency.
Hardness, by scratch against known references, done on an inconspicuous spot and not on a crystal face.
Streak, on an unglazed tile.
Cleavage and fracture.
Specific gravity, which is quantitative and undervalued.
Magnetism, fluorescence, and a dilute acid reaction for carbonates.
Each is cheap, each is partial, and together they usually get to a short list.
What the tests cannot do
Distinguish members of a solid solution series.
Separate species that differ only in structure.
Confirm a rare species, which is exactly where people most want confirmation.
For those the answer is instrumental analysis, which is available through university departments and commercial labs and is worth it for anything you intend to sell as a rarity.
Recording confidence
Write how you identified it, not just what.
"Visual", "hardness and streak", "XRD, 2026", "per the dealer, unverified" are all honest entries and they age far better than a bare name.
A label that states its own basis is more valuable than one that asserts, because the next person can judge whether to trust it.