Stone is not just stone.

Natural stone is one of the oldest building materials known to humanity, and remains one of the most versatile. Architects who specify stone make decisions about hardness, porosity, acid resistance, frost behaviour and aesthetic effect. This document summarises the most important stone types used in construction and interior architecture.

We distinguish between natural stone (formed geologically) and ceramic stone (industrially produced). Both have their place, but they behave fundamentally differently.

Measuring hardness: the Mohs scale.

Mohs hardness indicates how scratch-resistant a mineral is. The scale runs from 1 (talc, softest) to 10 (diamond, hardest). For practical interior fit-out purposes:

• Mohs 3–4: limestone, marble, travertine, dolomite, 'soft stones'. Sensitive to acids (lemon juice, vinegar, cleaning agents). Require impregnation.
• Mohs 6–7: granite, quartzite, 'hard stones'. Scratch-resistant, acid-resistant. Suitable for heavily used surfaces.
• Mohs 7+: quartzite, porcelain stoneware, extremely resistant. For floors, facades and exterior applications.

Limestone.

Limestone is a sedimentary rock consisting mainly of calcium carbonate (CaCO₃). It forms over millions of years from shells, corals and organic deposits in shallow marine environments. Limestone is one of the most widely used natural stones in construction.

Properties

• Mohs hardness: 3 (soft stone)
• Composition: primarily calcite, partly with clay, quartz and feldspar
• Surface: from polished-smooth to rustic, natural texture
• Application: floors, walls, staircases, facades, kitchen worktops (with impregnation)
• Note: reacts to acids; lemon juice, vinegar and acidic cleaners leave marks

Limestone offers a warm, earthy aesthetic and is available in tones ranging from white through beige and grey to dark anthracite. Well-known types: Jura Beige, Beige dei Medici, Chambolle, Pietra Serena, Ceppo di Gres.

Marble.

Marble is a metamorphic rock that forms from limestone under high pressure and temperature. In the process the calcite in the limestone recrystallises into a rock with a characteristic texture and veining. Recrystallisation eliminates the original fossils and sedimentary structures.

Properties

• Mohs hardness: 3–4 (soft stone)
• Composition: primarily calcite, with traces of mica, quartz and graphite (for the veining)
• Surface: polished high-gloss to honed matt
• Application: bathrooms, kitchens, floors, wall claddings, furniture surfaces
• Note: sensitive to acids and scratches; regular impregnation recommended

The most well-known marble types: Calacatta (warm white, expressive veining), Statuario (pure white, dramatic), Carrara (classic, fine-veined), Arabescato (boldly marked), Emperador Dark (deep brown).

Dolomite.

Dolomite resembles limestone but contains a significant proportion of magnesium carbonate. It is slightly harder than limestone (Mohs 3.5–4) and more resistant to weathering. In interior architecture, dolomite is often used as a premium alternative to marble, as it looks similar but is somewhat more durable.

Travertine.

Travertine is a limestone that forms at hot springs or in caves through the precipitation of calcium carbonate from mineral water. Its porous, textured surface with natural holes and depressions is its defining characteristic.

Properties

• Mohs hardness: 3–4
• Porosity: higher than other limestones; must be sealed
• Application: floors, walls, bathrooms, facades (filled or open)
• Colour range: ivory, walnut-brown, gold, grey

Travertine ages with a natural patina and gains character over time. For bathrooms and wet areas a sealant is essential.

Granite.

Granite is an igneous rock (plutonic) formed deep in the earth's crust by the slow cooling of magma. It consists mainly of quartz, feldspar and mica and is among the hardest and most resistant natural stones.

Properties

• Mohs hardness: 6–7 (hard stone)
• Composition: quartz, feldspar, mica, high silica content
• Surface: polished, flamed, satin, brushed
• Application: kitchen worktops, floors, facades, exterior applications
• Advantage: scratch-resistant, acid-resistant, frost-resistant, the most robust natural stone

Quartzite.

Quartzite is a metamorphic rock that forms from sandstone under high pressure and heat. It is extremely hard (Mohs 7) and resistant to abrasion and weathering. Quartzite combines the beauty of marble with the durability of granite.

Properties

• Mohs hardness: 7 (very hard stone)
• Composition: primarily quartz, with traces of feldspar, mica and iron oxide
• Surface: polished, honed or naturally split
• Application: kitchen worktops, heavily used floors, facades
• Colour range: white, grey, pink, green, often with dramatic veining

Well-known types: Taj Mahal Quartzite (warm gold, from Brazil), Super White (grey-white), Blue Roma.

Slate.

Slate is a fine-grained metamorphic rock that forms from mudstone under pressure. Its natural ability to split into thin slabs makes it ideal for roofing and wall cladding. In interior architecture it is used for floors, wall claddings and decorative elements.

• Mohs hardness: 3–4
• Surface: naturally split (rough), honed or satin
• Application: floors, walls, roofing
• Colour range: black, dark grey, green, purple

Belgian Bluestone.

Belgian Bluestone is a dense limestone with a characteristically blue-grey colour. Used in European architecture for centuries, it is frost-resistant, durable and available in more than 40 different surfaces, from polished to rustically aged.

• Mohs hardness: 3 (but dense and resistant)
• Frost-resistant: yes, suitable for interior and exterior applications
• Application: floors, walls, facades, kitchens, staircases, terraces
• Surfaces: Anticato, Vintage, Cottage, Flamé, Lappato and over 40 more

Bluestone is one of the few limestones that can be used in exterior applications without restriction.

Surfaces and finishes.

The surface finish influences not only the appearance but also the slip resistance, maintenance properties and durability of the stone.

• Polished: glossy, smooth. Emphasises colour and veining. Sensitive to scratches. Not slip-resistant.
• Honed: matt, velvety. The most common choice for floors. Less scratch-sensitive than polished.
• Flamed: rough, textured. Achieved by high-temperature treatment. Slip-resistant, ideal for exterior applications.
• Brushed: softly structured. Natural look with closed pores.
• Leathered: textured, natural. The surface retains character with closed pores.
• Sand-blasted: uniformly matt. Quiet surface for contemporary interiors.
• Bush-hammered: coarse, stippled. Traditional technique for facades and exterior stairs.

Care and impregnation.

All natural stones, especially the softer types (limestone, marble, travertine), benefit from professional impregnation. An impregnant penetrates the pores and forms an invisible protective barrier against oils and liquids, without impairing the stone's breathability.

Basic rules

• Cleaning: use only water and a mild cleaner (pH-neutral). Never use acidic cleaners.
• Impregnation: apply after installation and renew every 1–3 years (depending on use).
• Stains: blot immediately (do not rub). Liquids left to soak leave permanent marks on unsealed stone.
• Frost protection: only frost-resistant stones for exterior use (Bluestone, granite, quartzite).

Ceramic stone (porcelain stoneware / Porcellanato).

Alongside natural stone there is ceramic stone: industrially produced slabs of clay, feldspar and quartz, fired at over 1,200°C. Porcelain stoneware (also called Porcellanato) is extremely hard, virtually water-impermeable, frost-resistant and easy to maintain.

Advantages over natural stone

• Consistent quality: no natural variation, precise calibration
• Easy to maintain: no impregnation required, acid-resistant
• Frost-resistant: unrestricted exterior use
• More cost-efficient: often less expensive than premium natural stone

Disadvantages

• No natural variation: every slab looks identical, which can feel sterile
• Repair: damaged slabs must be fully replaced; natural stone can be ground
• Haptics: feels colder and more uniform than natural stone

In architectural practice, natural stone and porcelain stoneware are often combined: natural stone in representative locations (reception, bathroom, kitchen), porcelain stoneware in high-use areas (garages, utility rooms, exterior).

Selection and specification.

When selecting stone for a project, the architect should consider the following points:

• Use: floor (abrasion), kitchen worktop (acid), facade (frost)?
• Aesthetics: warm tones (limestone, travertine) vs. cool drama (marble, slate)?
• Budget: natural stone varies considerably in price, from CHF 80/m² (limestone) to CHF 600+/m² (Calacatta).
• Maintenance: is the client willing to maintain natural stone regularly? If not: choose porcelain stoneware or quartzite.
• Lighting: stone responds strongly to light. Always assess samples under the actual room lighting, not showroom light.
• Sample ≠ slab: a small sample never shows the full variation of a complete slab. Always select the slab itself.

Questions about stone selection for your project? Contact the supplier directly. You will find available stone types with contact details in our catalogue.