You already did
the tests.
Last updated: September 2026
Specific gravity, hardness, streak — the readings you take with a kitchen scale, a glass of water and a porcelain tile. Loupewise reads those numbers against a measured property table instead of guessing from a photograph.
How the readings you already take get used
A labeled example workflow — this is the intended use, not a customer story.
Weigh it wet and dry
Specific gravity is weight in air divided by the weight lost in water — a kitchen scale and a cup of water get you to two decimal places. Method here: how to measure specific gravity, or put the two weights straight into the SG calculator.
Add hardness and anything else you have
A Mohs pick set, a steel nail, a piece of glass. Enter the range you bracketed rather than a single guess — the engine takes ranges, and an honest 6–7 narrows better than a confident 6.5 that is wrong.
Read the surviving list
You get the species those readings do not rule out, ranked, plus the single next test that would split them. Where your numbers rule out everything, that is a real answer too: the material is outside this table.
The pieces that matter for rockhounds
Specific gravity chart
SG ranges for all 132 species in one sortable table — free, no account, and the same data the engine reads.
Measuring specific gravity
The hydrostatic method with a kitchen scale, the arithmetic, and the errors that move the third decimal place.
Mohs hardness chart
Hardness by species, with the common field testers — nail, glass, knife — placed on the scale.
The open dataset
The whole property table as CSV and JSON under CC BY 4.0. Take it, cite it, build on it.
The reference is free. Always.
The 132-species property tables, the instrument guides and the open dataset are free and need no account. Paid tiers exist for saving sessions and building a catalogue — not for seeing the answer.
Read this before you rely on it: Loupewise is a GEMSTONE database of 132 species and varieties — it is NOT a rock or mineral database. Most field finds are aggregates — jasper, chert, basalt, slag, concretions — and those are not in this table and never will be. It also has no streak, acid-reaction or locality fields, so it reads two of the five things on a rockhound checklist. If your find is a mystery rock rather than a cut or crystal gem species, mindat.org and r/whatsthisrock will serve you better, and that is not false modesty. Read our full methodology.
Put a reading in
Free, no account. If your numbers rule out everything in the table, you have learned something real.