Several popular "white quartzites" are actually dolomite — a stone between marble and quartzite in hardness. Dolomite is more durable than classic marble and often a great value, but it can etch. If you are paying for quartzite performance, confirm what the block really is.
| Quartzite | Dolomite | |
|---|---|---|
| Hardness (Mohs) | About 7 | About 3.5–4.5 |
| Scratches glass | Yes | No |
| Etching from acids | No | Can etch, usually less than marble |
| Sealing | Yes, about once a year | Yes, regularly |
| Looks | Wide range, often marble-like | Soft whites and greys, very marble-like |
| Typical price level | Mid to high | Often lower |
| Often sold as | — | "Quartzite" (e.g. Super White) |
Dolomite is a carbonate stone, like marble, but made mostly of the mineral dolomite instead of calcite. It is harder and less reactive than calcite marble, and white dolomites can look almost identical to white quartzites. Over time, "quartzite" became the selling label for some of them — most famously Super White, and some lots of Mont Blanc.
The glass test: drag a sharp corner of a sample across glass. True quartzite scratches it easily; dolomite will not. The acid test: put a few drops of lemon juice or vinegar on the polished face for ten minutes. Dolomite may show a faint dull spot; quartzite will not. Ask your supplier for a sample and do both.
Used for what it is, dolomite is excellent — tougher than Carrara, beautiful, and often well priced. The problem is only the mislabel. We tell you exactly what each block is, so you can choose dolomite on purpose or pick a true quartzite like White Macaubas.
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Super White is a dolomite, despite often being sold as "Super White Quartzite." It is harder than classic marble but softer than true quartzite and can etch.
True quartzite scratches glass; dolomite does not. Dolomite may also show a faint etch after lemon juice or vinegar sits on it for ten minutes.
It can, usually less than calcite marble. A honed finish hides etching better than polished.
It can be, if you accept that it may etch. It is more durable than classic marble. For a no-etch kitchen surface, choose a true quartzite.
