Optical Mineral Identifier

Optical Mineral Identifier is an offline petrography tool for thin section work. It takes observable optical properties from a polarizing microscope and ranks the most likely mineral matches using a weighted scoring algorithm.

It is not a replacement for a trained eye. It narrows the field; the user makes the final call.

WHAT IT DOES

You enter what you see under the microscope — birefringence, extinction angle and type, relief, pleochroism, cleavage, twinning, habit, body colour, and alteration. The algorithm scores each mineral in its database against your input, weighting properties by their diagnostic value (birefringence and extinction angle carry the most weight; body colour and alteration the least). It returns the top ten candidates ranked by confidence, with a 35% confidence floor below which it reports no match rather than guessing.

DATABASE

163 rock-forming and accessory phases, including:

— Silicates: quartz, full alkali feldspar and plagioclase series, micas, pyroxene and amphibole suites, olivine endmembers, garnet endmembers, the three Al₂SiO₅ polymorphs, epidote group, layer silicates
— Carbonates: calcite, dolomite, aragonite, siderite, rhodochrosite, magnesite, and others
— Oxides, halides, sulfates, hydroxides, borates, phosphates, tungstates, clays
— Common opaque phases (treated as isotropic in transmitted light)

Birefringence values cross-checked against Nesse's Optical Mineralogy, Deer Howie & Zussman, and Klein & Dutrow.

PRECISION MICHEL-LÉVY CHART

Built-in chart covering the 0–6000 nm retardation range, so high-birefringence carbonates and other phases are not compressed off the right edge of a standard chart.

OTHER FEATURES

— 100% offline, no account required, no tracking, no ads
— Dark mode for low-light lab environments
— SQLite database stored locally
— Built on .NET MAUI

ACCURACY AND LIMITATIONS

Internal testing indicates roughly 85-90% top-rank accuracy for clear-cut cases when all relevant properties are entered. Accuracy drops for ambiguous cases — plagioclase compositional varieties, amphibole subtypes, and similar fine distinctions where optical properties alone are insufficient.

The tool is a reference and screening aid, not an arbiter. Standard petrographic judgment remains necessary.

INTENDED USERS

Geology students learning thin section work, petrography researchers, and practising geologists who want a fast first-pass narrowing of candidates before consulting reference texts.

FEEDBACK

Misranks, missing phases, and bug reports are welcome at [email protected].