Relative of the calcite group

Magnesite belongs to the calcite carbonate group. Like calcite and dolomite, it is composed of rhombohedra and has perfect rhombohedral cleavage. The chemistry is simple — MgCO₃, but textures can be complex when it replaces earlier minerals.

Why jewelers often encounter it

Natural magnesite's porous, white "cloth" evenly absorbs dyes, so it often substitutes turquoise ("dyed magnesite", sometimes sold under creative names). It is beautiful on its own – in the form of clean white beads and cabochons with warm yellowish-brown veins.

Altered ultramafic rocks

In peridotite and dunite areas, CO₂-bearing solutions can replace magnesium-rich rocks (often through serpentinite) into magnesite veins and lenses. The result is pale, “chalky” veins with a yellowish network.

Hydrothermal and sedimentary origin

Magnesite also precipitates from Mg-rich brines and hydrothermal solutions, forming nodules, concretions, and crusts in cavities.

Replacement textures

Often replacing earlier carbonates or silicates, magnesite can inherit ghostly bands or brecciated patterns — a great visual accent for beads and cabochons.

Palette

• Chalk/bone white — classic appearance.
• Pale gray — in denser and crystalline areas.
• Honey yellow — iron-stained chips and healing cracks.
• Dyed blue/green — well-known turquoise incarnation.

Surface ranges from matte to softly satin. High gloss usually indicates a light wax/resin sealant due to porosity.

Pattern words

• "Spider web" — thin yellowish brown/gray veins.
• "Cauliflower" — nodular concretions with concentric growth layers.
• Brecciated — broken fragments, recemented with pale magnesite.
• "Porcelain" — clean white, veinless, for minimalist designs.

Photo tip: neutral, cool light (5000–5600 K) maintains a clean white. Low side light ~25–30° reveals subtle veins without glare.

Veins and pores

Look for small pores and soft yellowish-brown veins. Dyed stones often show color "concentration" in pores and along cracks.

Cleavage flashes

Freshly broken fragments show rhombohedral cleavage with a subtle glassy shine — classic carbonate behavior.

Acid hint (only on scraps)

A pinch of powder, touched with warm, very diluted acid, foams. Never try acid on finished jewelry — porosity and dyes won't appreciate it.

Halite

Other white, porous stone, often dyed blue. Differences: halite – borate (not prone to active foaming), lower SG (~2.5) and porcelain-like microstructure.

“White turquoise” / “White Buffalo”

Popular trade names; the material is usually magnesite/dolomite-rich rock, not turquoise. Luster and chemistry differ from real turquoise.

Marble and calcite

Softer (calcite – Mohs 3), often crystalline and obviously fizzes in cold acid. Magnesite fizzes slower in cold unless heated or ground.

Plastic and resin

Very light, warm to the touch, and may have a casting seam. Hot needle test (lab only) marks plastic — never do this with real stones.

Dolomite

Another carbonate; often shows “saddle” shaped crystals in geodes and reacts more sluggishly than calcite — similarly or variably like magnesite. Close cases are distinguished by lab tests.

Quick check

• Matte white with yellowish-brown veins + soft (≤4.5) + slow fizzing in cold → likely magnesite.
• Porcelain white, lighter, no fizzing → think halite.
• Strong fizzing in cold + glassier appearance → calcite/marble.

Where it occurs

Magnesite is widespread: in ultramafic belts and serpentinites, hydrothermal veins, and evaporite basins. Significant deposits are found in parts of Turkey, China, Greece, Slovakia, Austria, Brazil and Australia and elsewhere.

Not just for beads

In industry, magnesite is heated to obtain magnesium (MgO) for fire-resistant materials and special cements. In workshops, it is cut into beads, cabochons, spheres and often dyed for color play.

Daily care

• Clean with a dry or slightly damp soft cloth; avoid long soaking.
• Keep away from acids, vinegar, lemon, and aggressive cleaners.
• Keep separate; quartz, sapphire, and steel can polish the satin surface.

Jewelry guidelines

• Best for pendants, earrings, beads. For rings/bracelets choose protective edges and wear carefully.
• If dyed, limit sun/solvents and avoid ultrasonic/steam cleaning.
• Matte or polished metal settings highlight clean, modern white.

On wheels

• Work cool and gently; magnesite tends to split along veins.
• Pre-polish 600→1200→3k; finish with aluminum oxide on a soft pad — gentle satin light.
• For greater stain resistance and slightly higher gloss, coat with a thin, reversible microcrystalline wax layer.

Fizz test (only from scraps)

Place a pinch of powder from trimming into warm, very diluted acid — watch for slow fizzing. This is the signature of carbonates (do not try on finished pieces).

Weight and feel

Compare beads in your hand: magnesite feels heavier than howlite, cooler than plastic, and untreated it has a gently "chalky matte" feel.