Mineral Pigments

Part of Pigments and Paint

Processing mineral pigments from natural ore and rock sources.

Why This Matters

Mineral pigments are the most durable colorants available from natural sources. Unlike plant-based dyes that fade in sunlight or organic pigments that decompose, mineral pigments are inorganic compounds — metal oxides, sulfides, and carbonates — that resist light, heat, and chemical degradation. Cave paintings made with mineral pigments 30,000 years ago still show vivid color.

For a rebuilding community, mineral pigments provide the colors needed for permanent signage, waterproof coatings, ceramic glazes, and visual coding systems. Earth-tone minerals (ochres, umbers, siennas) are the most accessible, found in virtually every landscape. Brighter minerals (malachite, azurite, cinnabar) are rarer but produce colors no plant can match.

Mineral pigment processing also teaches ore identification and basic mineralogy — skills that transfer directly to metalworking, ceramic production, and chemical manufacturing. Learning to recognize iron oxides in the landscape means you can also find iron ore. Identifying copper carbonates means locating copper deposits.

Iron Oxide Pigments

Iron oxides are the most common and versatile mineral pigments. They produce the full range of earth tones: yellow, orange, red, brown, and black.

Yellow Ochre (Goethite/Limonite)

Yellow ochre is hydrated iron oxide (FeOOH) — iron rust with bound water molecules. It is the most abundant pigment on Earth.

Finding it:

• Look for yellowish-brown soil, clay banks, and streambed deposits
• Areas with iron-bearing rock often have ochre-stained water runoff
• Color ranges from pale yellow to deep golden
• Soft, earthy texture; marks on paper when rubbed

Processing:

1. Collect raw ochre clay or earth
2. Remove rocks, roots, and organic debris by hand
3. Crush to coarse powder in mortar
4. Levigate (suspend in water, let settle, collect fine fraction — see Levigation)
5. Dry the fine fraction on a flat surface
6. Grind on a slab with muller for paint-grade fineness

Red Ochre (Hematite)

Red ochre is anhydrous iron oxide (Fe2O3) — the same iron compound as yellow ochre but without water.

Natural sources:

• Red-stained soil and clay deposits
• Hematite nodules (dark metallic lumps that leave a red streak)
• Weathered iron-rich rock

Making red from yellow: Yellow ochre can be converted to red by calcination (heating):

1. Place yellow ochre in a fire-resistant container (clay pot, stone crucible)
2. Heat in a fire or kiln to dull red heat (approximately 300-400 degrees Celsius)
3. The bound water is driven off, converting goethite to hematite
4. Higher temperatures produce deeper reds; lower temperatures produce oranges
5. Cool slowly, then grind

Temperature Control

The exact shade of red depends on firing temperature. Make test batches at different heat levels to map the color range. Label and save samples for future reference.

Burnt and Raw Umber

Umber is iron oxide mixed with manganese dioxide, producing warm browns:

• Raw umber: Earthy greenish-brown, used as-is after levigation and grinding
• Burnt umber: Raw umber heated to 300-400 degrees Celsius, producing warm reddish-brown
• Look for dark brown to blackish-brown earth deposits

Sienna

Sienna is iron oxide with a lower manganese content than umber:

• Raw sienna: Warm yellowish-brown, translucent when ground fine
• Burnt sienna: Heated raw sienna, producing deep orange-brown
• Named for Siena, Italy, but found in iron-rich deposits worldwide

Mars Black (Iron Oxide Black)

Very dark iron oxide forms under reducing (low-oxygen) conditions:

• Found in bogs, swamps, and anaerobic clay layers
• Can be made by heating iron filings or rust in a sealed container (preventing oxygen access)
• Produces a warm, slightly brownish black — different from the cool black of charcoal

Copper Minerals

Malachite (Green)

Malachite is copper carbonate hydroxide (Cu2CO3(OH)2), producing a vivid green:

Identification:

• Bright green banded mineral, often in rounded masses
• Found near copper ore deposits
• Effervesces (fizzes) in vinegar or weak acid
• Hardness 3.5-4 on Mohs scale

Processing:

1. Crush carefully — malachite is moderately hard
2. Grind in mortar and pestle to coarse powder
3. Levigate to separate grades — medium particles give the richest green
4. Very fine grinding produces a paler, less saturated green
5. Use in oil or egg tempera binder; avoid lime (alkalinity can alter color)

Azurite (Blue)

Azurite is copper carbonate (Cu3(CO3)2(OH)2), producing a deep blue:

Identification:

• Deep blue crystal clusters, often found with malachite
• Same geological settings as malachite — copper deposits
• Also effervesces in acid

Processing:

• Same as malachite but even more sensitive to particle size
• Coarse grind: deep, rich blue
• Medium grind: bright blue (best for most painting)
• Fine grind: pale, washed-out blue
• Keep grinding time short once you reach desired color

Color Change

Over-grinding azurite turns it into a pale, nearly white powder. Check color frequently during grinding. Stop when color is at the shade you want.

Other Mineral Pigments

Cinnabar (Vermillion Red)

Cinnabar is mercury sulfide (HgS), producing a brilliant scarlet red:

• Found near volcanic/geothermal areas
• Extremely heavy, dense mineral
• Produces the most vivid natural red available
• TOXIC — mercury compounds are dangerous. Handle with extreme care, never heat in enclosed spaces, and wash hands thoroughly after handling

Orpiment (Yellow) and Realgar (Orange)

Arsenic sulfide minerals producing bright yellow and orange:

• Found near volcanic vents and hot springs
• HIGHLY TOXIC — arsenic compounds. Use only if no alternative exists, with extreme caution
• Process only outdoors with wind protection

Chalk/Whiting (White)

Calcium carbonate — the most accessible white pigment:

• Abundant limestone, chalk cliffs, seashells, eggshells
• Soft, easy to grind
• Not very opaque — requires many coats or thick application
• Excellent as an extender mixed with stronger pigments
• Chemically stable with all binders

Kaolin (White)

White clay mineral, softer and smoother than chalk:

• Found in weathered granite deposits
• Very fine natural particle size
• Good coverage when mixed with oil or lime binder
• Also essential for ceramics and paper coating

Processing Workflow

A standard workflow for processing any mineral pigment:

Raw mineral → Visual inspection (color, purity)
     ↓
Coarse crushing (hammer, mortar)
     ↓
Levigation (water separation into size fractions)
     ↓
Drying (shade, flat surface)
     ↓
Fine grinding (muller and slab, wet)
     ↓
Quality test (finger test, smear test, tinting test)
     ↓
Storage (labeled container, dry)

Color Palette from Common Minerals

A practical palette achievable from widely available minerals:

Color	Mineral Source	Availability
White	Chalk, kaolin	Extremely common
Yellow	Yellow ochre (limonite/goethite)	Very common
Orange	Calcined yellow ochre (low temp)	Made from yellow ochre
Red	Red ochre (hematite) or calcined yellow ochre	Common
Brown	Raw umber, raw sienna	Common
Warm brown	Burnt umber, burnt sienna	Made from raw forms
Black	Magnetite, bog iron oxide, manganese dioxide	Common
Green	Malachite, green earth (celadonite/glauconite)	Moderate
Blue	Azurite	Uncommon

With yellow ochre, red ochre, black oxide, and chalk white, you can mix a surprisingly complete range of earth tones. Adding green earth (a widespread, if dull, green mineral) expands the palette significantly.

Safety Considerations

Most earth pigments (ochres, umbers, siennas, chalk) are non-toxic and safe to handle. However:

• Avoid inhaling dust during dry grinding — all fine mineral dust is harmful to lungs over time
• Wet grind whenever possible to eliminate dust
• Mercury and arsenic minerals (cinnabar, orpiment, realgar) are acutely toxic — handle with extreme caution or avoid entirely
• Lead minerals (cerussite, galena) are cumulative poisons — avoid if alternatives exist
• Copper minerals (malachite, azurite) are mildly toxic if ingested — wash hands after handling
• Work outdoors or in well-ventilated spaces for all grinding operations