What is basalt stone, and can you use it in a bathroom?

What does basalt look like?

Dark gray to black, usually. The color comes from pyroxenes such as augite, and a lighter, plagioclase-rich variety is called leucobasalt. Weathered surfaces in humid climates turn brown to rust-red as iron oxidizes.

Tile suppliers describe charcoal as the most common variety, with blue-gray, near-black and an olive-toned stone sold as Ming Green. There is none of marble's dramatic veining; variation is subtle shifts in tone and the odd inclusion. Finishes: honed (smooth, matte), polished (high gloss, less common on dark stone), flamed (torch-roughened for grip) and brushed or sandblasted.

How does basalt perform on bathroom floors and shower walls?

Well, with a sealer. Its density and low porosity make it a durable floor and wall cladding, and tile retailers list floors, shower walls and countertops among its uses. The floor finish matters most: honed gives adequate grip, flamed gives more, polished the least.

It is not maintenance-free. A retailer says unsealed basalt can stain from standing water and absorbs oil readily, and recommends annual resealing. Dry the floor after use. Because basalt is dense, thin tiles can chip under heavy point loads, so thickness and substrate support matter. Check with a structural engineer and local code for floor loading on dense stone.

Does basalt need sealing?

A retailer advises a penetrating sealer before installation and resealing annually. A flooring guide says sealing is often recommended despite low porosity, mainly on polished surfaces and countertops, because it improves stain resistance and cleaning.

Clean with a pH-neutral stone cleaner or diluted mild dish soap. The retailer says never to use vinegar or citrus cleaners, claiming they etch the surface; as a silicate rock with no calcite basalt is unlikely to etch like marble, but acids and bleach can wear down a sealer, and the guide advises avoiding them for that reason. Skip abrasive scrubbers on a honed face.

How heavy is a basalt tub or sink?

Heavier than marble. Basalt averages about 2.9 g/cm³, which is about 181 lb/ft³, against about 168 for marble. Scaling our reference 67 × 31 × 22 in marble tub (about 1,150 lb empty) to basalt density gives roughly 1,240 lb empty. That is an estimate from density alone, not a quote.

See the stone bathtub weight guide for how weight and floor loading are worked out. Basalt tubs and basins are not covered by the sources opened for this page.

Where is basalt found?

Everywhere there has been large-scale volcanism. Basalt forms the main volcanic rock of oceanic islands such as Hawaii, the Faroe Islands and Réunion, and fills large igneous provinces including the Deccan Traps in India, the Paraná Traps in Brazil, the Karoo in South Africa and the Columbia River Plateau in the United States.

Thick flows crack as they cool into columns, mostly hexagonal; the Giant's Causeway in Northern Ireland and parts of Yellowstone are examples. The geology source does not name dimension-stone quarries, so ask any supplier for the quarry and a test report.

What is basalt confused with?

Honed black basalt is easily mistaken for slate, black granite or soapstone. Slate splits into thin layers, while basalt is massive and uniform. A tile supplier calls slate more layered and rustic and basalt denser and more architectural. Black marble such as Nero Marquina is veined in white and etches in acid, which basalt largely does not.

Does Pietra Fonte make pieces in basalt?

We don't currently offer basalt. We carve marble, travertine, onyx and a small range of other stones to order. See the stone library for what we work in, or write to us about a one-off piece through bespoke.