Guides · Materials

Quartzite or marble? Why a trade name does not tell you what you are buying

In short. The name on the quotation — Super White, Calacatta, Fantasy — is a market name, not a classification. It exists to sell a slab, not to tell you how it will behave in your house. Two stones with almost the same name can react in opposite ways to a glass of wine. Two tests settle most of it in thirty seconds, and four pieces of data settle it for good.

What should the name of a stone actually tell you?

A European standard answers that: EN 12440, Natural stone — Denomination criteria, which establishes the criteria for designating natural stone from raw material to finished products. And it says something almost nobody observes: the name on its own is not the denomination.

The standard calls for four elements together. The traditional or commercial name — the name under which the stone is marketed, corresponding to a particular type of rock and a specific place of origin, with an express recommendation to avoid geographic names unrelated to the real origin, and company names. The petrological family, the scientific name of the rock, obtained by petrographic examination according to EN 12407 and EN 12670. The typical colour. And the place of origin, as precise as possible: at least city or village, municipality, province and country.

When a quotation carries only the first of the four, you are not reading a denomination. You are reading a brand.

Companies around the world often use invented names to identify stones: the name is there to sell the slab, not to say what the rock is. It is common practice, and not always in bad faith — but it is why the name on its own is never the answer to the question you are asking.

Why «granite» and «marble», commercially, are not geological families

Because trade groups stone by how it behaves, not by how it formed. The Natural Stone Institute says so openly: about ten groups are acknowledged commercially, and the granite group takes in most igneous rocks — gabbro, diabase, anorthosite, sodalite, gneiss, basalt and many others — because they behave and perform similarly to granite. Two examples they cite themselves: Paradisio is commercially granite and geologically gneiss; Absolute Black is commercially granite and geologically gabbro.

The same works in the other direction: the marble group takes in dense or partly metamorphosed limestones, particularly those capable of taking a polish. Crema Marfil, sold everywhere as marble, is geologically a limestone.

None of this is a swindle; it is a trade convention, and for many decisions it works. It becomes a problem in one precise case, which is the next one.

Why confusing marble with quartzite is expensive

Because here the two stones do not behave alike at all, and the difference shows on day one.

Marble is made of calcite, and calcite is dissolved by acids: vinegar, lemon, wine, citrus, the wrong cleaner. The result is not a stain but an etch — a dull halo where the polish has been eaten away. Quartzite is made of quartz, and quartz is not affected by common acids.

There is a middle case that complicates matters: dolomitic marbles. Dolomite is chemically similar to calcite and is affected by acids too, only not as quickly. And it is precisely the white stones of this family that are most often presented as quartzites: Super White and Calacatta Gold, two names that circulate widely, are marble breccias.

On the Mohs scale the distance is stark: calcite is point 3, quartz is point 7. That is not a nuance.

How do you tell quartzite from marble?

With two tests, run on an offcut — never on the finished piece, and never on a visible area.

One useful note on the knife test: if drawing the blade leaves a silvery line that rubs away, that is not a scratch in the stone — it is metal deposited on the surface. On a true quartzite, that is what happens.

If in doubt, the acid test is the more honest of the two, because it measures exactly the fault that will bother you at home.

And «quartz»? It is not the same as quartzite

It is not, and the confusion is daily, because the two words look alike.

Quartzite is a natural stone: a sandstone transformed by heat and pressure, quarried and cut into slabs. The quartz of kitchen tops is an engineered material: quartz grains held together by a resin binder, produced in a plant as identical slabs. It is not natural stone, and it does not fall under the denomination rules of EN 12440 at all.

This is not a judgement of value — engineered material has its advantages, starting with uniformity. They are two different products, and each should be chosen knowingly.

What to ask for, instead of the name

Four things, all of which a serious supplier already has.

The petrographic examination to EN 12407: the document that states what the rock actually is, and ends every argument about the name. The water absorption to EN 13755: it says how much the stone drinks, and it is the figure that matters if the piece will live outdoors or in a bathroom. The flexural strength to EN 12372: it says how the top behaves in overhang, and together with thickness decides whether a long table can be made at all. The abrasion resistance to EN 14157, for surfaces that will be used every day.

One honest distinction about who needs which document. On the blocks we buy at the quarry the origin does not have to be reconstructed, because we know it from the first step: the petrographic examination describes the rock, it does not tell us where it came from. The advice to ask for petrological family, colour and place of origin applies above all to anyone buying a slab already sawn by somebody else: that is where a trade name, on its own, is not enough.

If all that arrives is a photograph and an evocative name, the right question is not «which marble is this» but «which petrological family, and which quarry».

What if all I have is a photograph?

It is the commonest case of all, and it resolves better than you would think.

People often arrive with a photograph and a name they read somewhere. The photograph is enough for us: we tell them which stone it is. And because the blocks are ours, they can then choose the slab closest to what they had in mind without the price changing — the choice is about taste, not about the price list.

That is the difference between buying a name and buying a stone. The name of a slab can only be chosen from among those somebody decided to print on a price list; a slab is chosen by looking at it.

Does any of this change for a table?

It changes a good deal, because a table combines two problems that stay separate in a kitchen top: it is seen from every side, and it works in overhang beyond its base.

On everyday behaviour, everything above applies: on a marble table a glass of spilled wine left to sit will leave its mark; on a quartzite it will not. Why an etch and a stain are two different kinds of damage is set out in marble stains and etching.

Structurally, thickness and support matter more than the family: the numbers are in how thick a marble top should be. Weight changes with the family too, and with it what has to carry the piece: the arithmetic is in how much a stone top weighs. And if the table is going outside, the choice narrows: quartzites are the family that copes best outdoors, as we explain in can a marble table live outdoors?

One thing worth knowing about price: the name weighs more on the price list than it does on performance. A stone with a fashionable name costs more than an equivalent one with a less familiar name. How the price is built up is set out in how much a custom marble table costs.

How we work

Stoneform makes tables, tops and works in marble, onyx and natural stone. We buy blocks directly at the quarry and saw the slabs ourselves, in our own factory. When a stone is not available to us as a block, we buy the slabs from importers we trust. Before cutting, every slab is examined against the light, to see how it is made inside before deciding where the cut falls. We do not use resin to reinforce slabs; on large surfaces a support helps, and the mesh on the back is already a good support in itself.

On price, the same logic as the name applies: it pays to go to whoever makes the piece. Retailers apply a mark-up of 35-50% on the maker's price, and buying from someone who imports the stone directly saves a further 20% or so. A 240 cm marble table costs around 3,800 euro: the price depends on dimensions and finish, and smaller does not automatically mean cheaper. These are orders of magnitude, not a price list.

Our pieces are in the tables collection and among our works; for projects, the Contract page explains how we handle commissions. Stoneform and Brianform are two divisions of the same company: from stone to upholstery the service is complete, with no intermediaries and with in-house production. Start from a drawing or an idea: write to us.

Frequently asked questions

How do I know whether mine is really quartzite?

Two tests on an offcut: a drop of acid, which leaves nothing on quartzite and a dull mark on marble; and a point against glass, which quartzite scratches and marble does not.

Is Super White a marble or a quartzite?

Super White and Calacatta Gold are cited among marble breccias. The trade name alone is not enough: ask for the petrological family.

All I have is a photograph — can you tell what stone it is?

In most cases, yes. Send us the photograph and we will tell you which stone it matches; the slab is then chosen from those our blocks can yield.

Are quartz and quartzite the same thing?

No. Quartzite is natural stone taken from a quarry; the quartz of kitchen tops is an engineered material of grains held together by resin, produced in a plant.

Why do two stones with the same name cost different amounts?

Because a trade name does not identify a quarry. EN 12440 asks for petrological family, colour and a precise place of origin alongside the name: that is where the difference shows.

Does dolomitic marble resist acids?

Less than people expect. Dolomite is chemically similar to calcite and is affected by acids too, only more slowly.

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The standards referred to are EN 12440 for the denomination criteria of natural stone, EN 12407 and EN 12670 for petrographic examination and terminology, EN 13755 for water absorption, EN 12372 for flexural strength and EN 14157 for abrasion resistance; the hardness of calcite and quartz is given on the Mohs scale. The trade-group examples quoted (Paradisio, Absolute Black, Crema Marfil, Super White, Calacatta Gold) come from the published industry literature. The prices quoted are orders of magnitude and do not constitute a quotation. Every project should be checked against the chosen slab and its technical data sheet.