Mineral identification · Diagnostic field testing
Five tests.
Then a name.
Master mineral identification in the field. A 5-step diagnostic protocol, regional South Okanagan and Similkameen profiles, and a calm comparison of native gold and pyrite.
“Dug by Hand. Crafted by Heart.” · “Fall 7, Stand 8.”
The 5-step physical diagnostic protocol
Effective field identification requires a systematic approach to narrow chemical and structural properties. Run these five tests in the same order so Tuesday’s notes can still speak to Friday’s.
Before you scratch anything: what would have to be true for this stone to be quartz? What would have to be true for it to be calcite? Write those two predictions. Then test.
Step 1: Mohs scratch hardness
The Mohs scale measures resistance to being scratched. In the field, common objects approximate hardness:
- Fingernail (~2.5) — scratches soft minerals like gypsum or talc.
- Copper penny (~3.5) — scratches calcite but not fluorite.
- Pocket-knife steel blade (~5.5) — scratches glass and some silicates.
- Unglazed glass plate (~6.5) — used to test harder minerals.
Microcrystalline quartz varieties — jasper, chert, and chalcedony — typically test between 6.5–7.0. They scratch glass easily and resist a steel knife. If a “jasper” dents under a blade, what else might it be?
Step 2: Streak testing
Streak is the color of a mineral in powdered form, often more consistent than the color of the external specimen. Drag the mineral across an unglazed porcelain tile:
- Hematite — characteristic reddish-brown streak.
- Pyrite — greenish-black streak.
- Native gold — distinctive golden-yellow streak.
Ask: if the hand-specimen is brassy and the streak is black, which color is telling the truth?
Step 3: LED translucency & edge-lighting
Hold a high-output white LED against the stone or inspect thin margins:
- Translucent — light passes through the edges. Hallmark of chalcedony and agate.
- Opaque — light is completely blocked. Typical of siltstone, argillite, or dense chert.
Step 4: Longwave UV fluorescence (365 nm)
A 365 nm UV light can reveal hidden mineralogical data. Fluorescent responses often indicate secondary mineral deposition. Calcite veining often fluoresces white, yellow, or red. Inert silica typically does not react. Use this to separate a carbonate vein from a silica body that only looks similar in daylight.
Step 5: Dilute acid reaction (fizz test)
A drop of dilute hydrochloric acid — or household vinegar, more slowly — tests for calcium carbonate. Watch for effervescence.
- Carbonates (calcite / limestone) — vigorous fizz.
- Silicates — remain inert, no visible reaction.
Handle acid as a field chemical, not a toy. A drop is enough. Neutralize and pack the bottle out. Never test a finished jewelry face.
| Test | Tools | What it tells you |
|---|---|---|
| Mohs hardness | Fingernail (~2.5), copper penny (~3.5), steel knife (~5.5), glass plate (~6.5) | Separates silicates (often 6.5–7.0) from softer carbonates and alteration minerals. |
| Streak | Unglazed porcelain tile | Hematite: reddish-brown. Pyrite: greenish-black. Gold: golden-yellow. |
| Translucency | High-lumen LED, edge lighting | Opaque chert or siltstone versus translucent chalcedony and agate. |
| UV fluorescence | 365 nm UV light | Secondary mineralization and calcite veining versus inert silica. |
| Acid reaction | Dilute HCl or vinegar | Vigorous fizz points to calcite or carbonate matrix. No reaction points to silicates. |
Place
Regional species profiles of the South Okanagan & Similkameen
The geological diversity of the South Okanagan and Similkameen offers specimen-grade minerals. After you run the five tests, ask which local family the results actually fit.
Red & polychrome jasper
Microcrystalline silica colored primarily by iron oxides. Conchoidal (shell-like) fracture. Mohs hardness 6.5–7.0. Polychrome varieties exhibit swirling patterns of red, brown, and tan.
Okanagan golden & yellow jasper
Distinct from red varieties. Color comes from limonite infusions within the cryptocrystalline quartz matrix. Warm, earthy saturation. Sought after for that reason — still test hardness before you call it jasper.
Chalcedony & agate
Fibrous quartz varieties recognized by waxy luster and translucent edges. Agates are the banded members, formed by rhythmic deposition in volcanic or sedimentary cavities.
Black chert, argillite & siltstone
Fine-grained sedimentary and metasedimentary rocks, often dark from organic carbon. Generally opaque. They lack the waxy luster of true chalcedony — edge-lighting makes that difference visible.
Optical calcite / Iceland spar
Rhombohedral cleavage. Double refraction: objects viewed through a clear piece appear doubled. Mohs hardness 3.0. Reacts vigorously to the acid fizz test. Softness plus fizz is not quartz, no matter how clear the crystal looks.
Galena & sulfide ores
Often found in historical mining districts. Galena is identified by brilliant metallic luster, high density (heavy for its size), and perfect cubic cleavage that breaks into distinct 90-degree steps. Treat sulfides as specimens first.
Diagnostic master table: real gold vs. pyrite & common sulfides
If two grains share a brassy color, which single test would you run first — and why that one, not hardness, not heft?
| Criteria | Native gold (Au) | Pyrite (FeS2) | Chalcopyrite (CuFeS2) | Arsenopyrite (FeAsS) |
|---|---|---|---|---|
| Color & tarnish | Golden yellow; no tarnish | Pale brassy yellow; may tarnish brown | Brassy to “peacock” iridescent | Silver-white to steel grey |
| Crystal habit | Nuggets, grains, or wires | Cubic or pyritohedral | Massive or tetrahedral | Tabular or prismatic |
| Mohs hardness | 2.5–3.0 | 6.0–6.5 | 3.5–4.0 | 5.5–6.0 |
| Streak color | Golden yellow | Greenish-black | Greenish-black | Grey-black |
| Malleability | Malleable; indents smoothly | Brittle; shatters / powders | Brittle; crumbles | Brittle; shatters |
| Magnetism | Non-magnetic | Usually non-magnetic | Weakly magnetic when heated | Non-magnetic |
| Specific gravity | 19.3 (extremely high) | 5.0 (moderate) | 4.2 (moderate) | 6.0 (moderate-high) |
A dent test belongs on a loose grain, not on a specimen you intend to keep intact. When in doubt, leave the piece whole and write the uncertainty on the card.
Field lapidary potential assessment
Before committing a specimen to the saw or tumbler:
- Micro-fractures. Inspect for internal checks that may shatter the stone during cutting.
- Structural cohesion. Ensure the stone is not crumbly or vuggy (full of small holes) unless that texture is the desired aesthetic.
- Softness gradients. In multi-mineral stones, one part significantly softer than another leads to uneven polishing.
- Surface rind. Evaluate how thick the weathered exterior is, and how much material must be removed to reach the heart of the stone.
Join the community
Found something unique in the hills? We want to see it — after you have written the tests, not instead of them.
Identify your finds
Send photos and test results of unidentified local finds. Include hardness, streak, light, UV, and acid if you ran them.
Contact the studio ↗Source verified specimens
Browse professionally identified and ethically sourced mineral specimens in the shop.
Open the shop ↗Printable studio paper
The same protocol as Guideline 08, ready to print or save.
Open file ↗