What is serpentine stone?
Serpentine stone is a greyish-green to almost black-green natural stone with marble-like veining, sold under names such as serpentine, serpentino or “green marble”. Geologically it is serpentinite, a metamorphic rock formed when ultramafic rock from the Earth’s mantle, such as peridotite, reacts with water and is converted into minerals of the serpentine group. Despite the trade name, it is not a true marble.
Properties
- Colour and pattern: green in many shades, often with pale veins. Varieties with a lot of calcite veining are often sold as verde antique.
- Relatively soft: the serpentine minerals themselves have a Mohs hardness of about 2.5 to 3.5, far softer than granite. It is easy to work and polish, but scratches and wears more readily.
- Not marble: marble is metamorphosed limestone; serpentinite is altered mantle rock. Care is similar, the material behaves differently.
Application
Serpentine is used for floor and wall tiles, window sills, thresholds, stair treads, fireplace surrounds and interior cladding, and occasionally for facades. Points to watch:
- Moisture-sensitive during fixing. Many green serpentines warp or curl when they absorb water from the adhesive. Use a rapid-setting or low-water adhesive (such as epoxy) as recommended by the supplier, not a standard cement-based tile adhesive.
- Choose carefully for outdoor use. Some varieties weather outside, lose their polish or discolour. For facades and exterior work, ask for technical data and reference projects for the specific stone.
- Avoid acids. Calcite-rich varieties in particular are etched by vinegar, lemon juice and limescale removers. Clean with pH-neutral products and seal where appropriate.
- Stair treads: polished serpentine is slippery; a honed or brushed finish is safer.
Take care when cutting and grinding
Chrysotile (white asbestos) is also a serpentine-group mineral, and some serpentinite deposits contain it. Commercial stone normally comes from suitable quarries, but always cut wet, with dust extraction and a P3/FFP3 respirator. With old stone of unknown origin, have a sample tested before grinding or breaking it out.
Related terms
- Marble
- Granite
- Natural stone finishes
- Asbestos
- Hairline fissures in natural stone
- Window sill
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