Making Malachite Green Pigment — Grinding the Copper Mineral into Painter's Green

Examine the raw malachite ore and select pieces with the most vivid, saturated green colour. Discard any pieces with brown iron staining, white calcite inclusions, or dull grey-green areas — these impurities will muddy the final pigment. Pure malachite is a rich green with the characteristic banded or botryoidal (grape-like) structure. Rinse the selected pieces in clean water and scrub with a brush to remove surface dirt and loose rock. Let dry completely before proceeding.

Place the cleaned malachite pieces in a heavy stone mortar and crush to coarse fragments (2-5 mm) with firm, straight-down blows — do not grind in circles yet. The goal is to break the mineral into small pieces without over-grinding. Malachite is relatively soft (Mohs hardness 3.5-4) and crushes easily. Work in small batches to maintain control over particle size. Remove any non-green fragments or impurities that become visible as the pieces break apart.

Transfer the coarse fragments to a flat glass slab and grind with a glass muller using small circular motions. Add a few drops of water to help the grinding (wet grinding reduces dust and improves particle breakdown). Grind to a medium-fine consistency — the particles should feel slightly gritty between your fingers, not silky-smooth. DO NOT over-grind: malachite that is ground too fine loses its vivid green and becomes a pale, washed-out greenish-white. Check the colour frequently by smearing a small sample thinly on white paper.

Place the ground malachite in a tall glass jar and add clean water — approximately 10 parts water to 1 part pigment. Stir vigorously and let stand. The heaviest (coarsest) particles settle within 30 seconds — these are too coarse and dark. After 30 seconds, carefully pour the still-cloudy water into a second jar, leaving the coarse sediment behind. Let the second jar settle for 5-10 minutes — the medium particles that settle during this time are the ideal pigment fraction with the brightest green. Pour off the remaining cloudy water into a third jar (this ultra-fine fraction will be pale). Repeat the process 2-3 times to wash out any soluble impurities.

Let each levigation fraction settle completely (overnight is ideal). Carefully pour off the clear water without disturbing the sediment. Spread the wet pigment paste in a thin layer on a clean, non-absorbent surface (glass or glazed ceramic) and let dry completely at room temperature — 1-2 days. Once dry, the pigment forms a hard cake that breaks apart easily. Gently crumble into a powder and store in a sealed glass jar away from direct sunlight. Label each fraction by settling time. The medium fraction is the primary painting pigment; the coarse fraction can be re-ground; the fine fraction is useful for tinting and glazing.