Natural Stone
Natural stone is quarried rock cut to shape with diamond tooling — igneous granite and basalt, metamorphic marble, quartzite, slate and soapstone, sedimentary limestone, sandstone and travertine — specified for mass, flatness, permanence and appearance rather than strength per weight. Granite runs 2.6–2.8 g/cm³ with a compressive strength of 130–250 MPa, a Mohs hardness of 6–7 and water absorption below 0.4 %, which is why lapped granite is the reference surface for flatness in every machine shop; marble and limestone are softer calcite rocks (Mohs 3) that carve and polish but etch in acid; slate splits into thin flat sheets; soapstone is inert, heat-storing talc that works with woodworking tools. Every stone is brittle, with a flexural strength around a tenth of its compressive strength, and varies bed to bed, so structural use relies on tested lots and generous safety factors.
Popular natural stone grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| Granite | — | 12 | 2.68 | Poor | — | Surface plates, machine bases, countertops, cladding |
| Marble | — | 8 | 2.7 | Good | — | Carving, interior cladding, polished feature stone |
| Quartzite | — | 17 | 2.65 | Not recommended | — | Granite-hard, acid-proof worktops and paving |
| Slate | — | 16 | 2.8 | Good | — | Roofing, flooring, flat splittable insulating sheet |
| Soapstone | — | 10 | 2.95 | Excellent | — | Lab benches, sinks, stove surrounds |
| Limestone | — | 5 | 2.4 | Very good | — | Carved masonry, architectural elements, paving |
| Basalt | — | 15 | 2.9 | Not recommended | — | Densest, most abrasion-resistant dark paving |
Choose natural stone for
Surface plates, straightedges, squares, machine bases and metrology fixtures; countertops, benches, sinks and lab furniture; cladding, paving, steps and copings; memorials, sculpture and carved architectural elements; fireplaces, stoves and heat-storage masses; and any part where mass, damping, permanence and a natural surface are the specification.
Look elsewhere when
The part is loaded in tension or bending without steel or fiber reinforcement (stone flexural strength is a tenth of compressive and it fails without warning — use Granite in compression or as a plate on a stiff base), the thickness is under about 20 mm over a span (a ceramic tile or a stone-veneer honeycomb panel), tight tolerances are needed on anything but a flat lapped face (machined aluminum or steel), it must be light or portable (a cast mineral or epoxy-granite composite), or it will see acid, wine or citrus on a calcite stone (Quartzite or Granite instead of Marble, Limestone or Travertine).
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Natural stone by application
- Surface plates and machine bases
- Black Granite (gabbro or diabase) lapped to Grade AA, A or B flatness; a 1000 × 630 mm plate is ground flat within a few microns and damps vibration a cast-iron plate rings with. Threaded inserts are epoxied in, never tapped.
- Countertops and lab benches
- Granite or Quartzite for kitchens and workshops; Soapstone for chemistry benches and sinks, where acids and hot glassware are routine; Marble only where its look is worth the etching and staining.
- Cladding, paving and steps
- Granite, Quartzite, Basalt and dense Sandstone for exterior work and traffic; Limestone and Travertine for sheltered facades and interiors; Slate for floors and roofs that must shed water for a century.
- Carving and memorials
- Marble and Limestone carve with hand and pneumatic tools and take fine detail; Granite carves slowly but weathers unchanged; Soapstone and Onyx for small objects and backlit panels.
Working with natural stone
- Cutting and machining
- Stone is sawn with diamond blades and wire, drilled with diamond core bits and CNC-milled or profiled with diamond tooling — always under water for cooling and dust control. Bridge saws and waterjet cut slabs to ±1 mm; CNC profiling holds ±0.5 mm on edges and pockets; lapping brings a granite face flat within a few microns over a metre. Hardness sets the speed: Soapstone and Marble cut several times faster than Granite and Quartzite. Silica dust from granite, sandstone and quartzite is a respirable hazard, so wet cutting and extraction are non-negotiable.
- Joining and fixing
- Epoxy and polyester stone adhesives bond stone to stone and to steel; mechanical fixings are stainless pins, dowels, undercut anchors and kerf clips in the back of cladding, never fasteners through thin sections. Threaded inserts are epoxied into cored holes; loads are carried in compression wherever possible, with steel angles and frames taking the tension and bending. Countertop seams are epoxied and colour-matched; slate splits along its cleavage and is nailed or hooked, not glued.
- Finishing
- Polished (mirror gloss), honed (matt smooth), flamed, bush-hammered, sandblasted, brushed and split-faced finishes all come from the same slab; polish shows the colour, textured finishes give slip resistance outdoors. Porous stones — Sandstone, Limestone, Travertine and many marbles — are sealed with a penetrating impregnator against staining; calcite stones still etch under acid regardless of sealer. Granite and Quartzite need no sealer beyond kitchen use.
- Movement and moisture
- Stone does not move with humidity as wood does, but it expands thermally at 5–10 ppm/K — a 3 m dark granite facade panel grows about 2 mm from winter shade to summer sun — so cladding sits on ventilated rainscreen fixings with movement joints. Porous stones absorb 2–10 % water and can spall in freeze-thaw; dense granite, quartzite, slate and basalt are frost-proof. Iron-bearing marbles and some granites rust-stain when wet; efflorescence appears where mortar salts migrate through limestone.
Other natural material series
Natural Stone — frequently asked
What is natural stone?
Natural stone is quarried rock cut to shape with diamond tooling — igneous granite and basalt, metamorphic marble, quartzite, slate and soapstone, sedimentary limestone, sandstone and travertine — specified for mass, flatness, permanence and appearance rather than strength per weight. Granite runs 2.6–2.8 g/cm³ with a compressive strength of 130–250 MPa, a Mohs hardness of 6–7 and water absorption below 0.4 %, which is why lapped granite is the reference surface for flatness in every machine shop; marble and limestone are softer calcite rocks (Mohs 3) that carve and polish but etch in acid; slate splits into thin flat sheets; soapstone is inert, heat-storing talc that works with woodworking tools. Every stone is brittle, with a flexural strength around a tenth of its compressive strength, and varies bed to bed, so structural use relies on tested lots and generous safety factors.
Which grade of natural stone should I use?
Granite for surface plates, machine bases, metrology fixtures, countertops and exterior cladding — the black gabbros and diabases sold as granite are the densest and stiffest for surface plates, the lighter feldspar granites for architectural work. Quartzite when the surface must be as hard as granite but paler and acid-proof, or must resist sliding abrasion in paving and worktops. Marble for carving, sculpture, interior cladding and fireplaces where a fine polish and translucency matter more than acid resistance. Slate for roofing, flooring, blackboards, pool tables and switchboard bases — flat, splittable, low absorption and electrically insulating. Limestone and Sandstone for carved architectural elements, masonry and paving where a soft, workable, matt stone is wanted; Travertine for interior floors and cladding with its pits filled; Onyx for backlit feature panels and small objects. Soapstone for laboratory benches, sinks, stove surrounds and heat-storage masses that shrug off acids and thermal shock. Basalt for the darkest, densest, most abrasion-resistant paving and liners.
Which grade of natural stone is easiest to machine?
Soapstone (machinability excellent, 90/100), then Limestone (80/100).
Why is granite used for surface plates instead of cast iron?
Because it is denser, non-magnetic and does not rust, ring, burr or warp: a lapped black granite plate holds Grade AA flatness of a few microns for decades, damps vibration instead of transmitting it, and a nick leaves a harmless pit where cast iron raises a burr that throws off every measurement after it. Cast iron still has its place for magnetic chucks and for plates that must be scraped in place, but for reference flatness granite won a century ago.
Granite or quartzite for a worktop?
Both are hard (Mohs 6–7), dense and acid-resistant, and both cut and polish with the same diamond tooling. Granite gives the broader colour range, the black gabbros for a dark polished look, and needs little or no sealing. Quartzite is a metamorphosed sandstone: paler, often veined like marble, marginally harder and more abrasion-resistant, but some slabs are porous enough to want a sealer, and stone sold as soft quartzite is sometimes a dolomitic marble that will etch — test with a drop of vinegar before buying.