Making Green Earth Pigment (Terra Verte) — The Soft Green of Celadonite and Glauconite

Examine the raw green earth mineral and select pieces with the most saturated green colour. Celadonite (from volcanic sources) is typically a deeper, bluer green; glauconite (from marine sandstones) is more olive-dull green. Discard any pieces with significant brown iron oxide staining, white quartz inclusions, or grey clay contamination — these impurities dilute the green and muddy the final pigment. Break or crumble the mineral into small pieces (1-2 cm) for easier grinding. Green earth minerals are typically very soft (Mohs hardness 2-3) and crumble easily between your fingers.

Place the sorted mineral pieces in a mortar and grind with a pestle. Green earth is one of the softest mineral pigments and breaks down very quickly — it practically crumbles under the pestle. Grind until no visible fragments remain and the powder feels uniformly fine. Unlike malachite (which loses colour when ground too fine), green earth can be ground as fine as possible — the colour remains stable at all particle sizes because it is an inherent property of the crystal structure, not a particle-size-dependent effect.

Place the ground powder in a tall glass jar and add clean water at approximately 10:1 ratio (water to pigment by volume). Stir vigorously for 2-3 minutes, then let settle. Heavy impurities (sand, quartz, rock fragments) settle in the first 10-20 seconds — pour off the still-cloudy green suspension into a second jar immediately. Let the second jar settle for 1-2 hours — the green earth particles settle as a soft, velvety green layer. Pour off the clear water above. Repeat the wash 2-3 times with fresh water to remove any soluble salts or clay impurities. The levigation also homogenises the pigment, producing a more uniform colour.

After the final wash, let the pigment settle completely (overnight is ideal). Carefully pour off as much clear water as possible without disturbing the sediment. Spread the wet pigment paste in a thin layer on a clean glass or glazed ceramic surface and let dry completely at room temperature — 1-3 days depending on humidity and layer thickness. Do not dry in direct sunlight or with heat, as this can cause uneven drying and caking. The dried pigment will form a soft, earthy cake that crumbles easily.

Crumble the dried pigment cake and give a final grinding with a glass muller on a glass slab to ensure uniformity. Green earth grinds to a silky, smooth powder with very little effort. Pass through a fine mesh sieve to remove any remaining coarse particles. The finished pigment should be a uniform, soft green powder — muted and earthy, not vivid. Store in a sealed glass jar away from moisture. Green earth is ready to mix with any binder: gum arabic for watercolour, egg yolk for tempera, linseed oil for oil paint, lime water for fresco, or beeswax for encaustic. It is especially valued as an underpainting green (verdaccio) for flesh tones in egg tempera.