"Quartzite" is the most abused word in the stone business. Two slabs sold under the same name, from two suppliers, can be different rocks with different behavior. Here's how to tell what you're actually buying.
What real quartzite is
Sandstone buried deep enough, hot enough and long enough that the quartz grains recrystallize and fuse. The result is dense, silica-based and hard — 7 on the Mohs scale, harder than granite. It doesn't etch from acid, because there's no calcium carbonate in it to dissolve.
Why the label gets stretched
Metamorphism is a spectrum, not a switch. A block can be partly converted: some quartz, some remaining carbonate. That material looks like quartzite, cuts like quartzite, and gets sold as quartzite — but it etches like marble, because part of it still is.
It's not usually fraud. The quarry, the exporter and three intermediaries all repeat what they were told, and the trade name travels further than the geology.
The lemon test
Put a drop of lemon juice on a sample, leave it fifteen minutes, wipe it off.
- Nothing happens: true quartzite.
- Dull spot: there's carbonate in it. Treat it as a marble for maintenance, whatever the label says.
Any supplier who won't let you do this on a sample is telling you something.
The scratch test
Real quartzite scratches glass. Marble doesn't. Take a scrap of the stone to a piece of glass and press hard. If the stone marks the glass, the quartz content is real.
Names that get applied loosely
Some of the most popular "quartzites" in the market are debated among fabricators. Taj Mahal, Fantasy Brown, Super White and Calacatta Macaubas all appear under different classifications from different sellers. Super White in particular is sold variously as quartzite, dolomite and marble — and in most cases it is a dolomitic marble, which is why it etches.
This is why you'll see the same stone typed differently across websites, including sometimes within one catalog. It reflects genuine disagreement in the trade, not carelessness.
What to ask before you buy
- Is this a true quartzite, or a dolomitic marble sold as one?
- Has anyone acid-tested this block?
- What country and quarry did it come from?
- Can I put lemon juice on the sample?
A distributor who has handled the block can answer all four. One who is reading a label can't.
Does it matter?
Only if you'd be upset by etching. A dolomitic marble sold as quartzite is still a beautiful stone — it just needs marble care. The problem isn't the material, it's buying it while expecting something else.
Want to know what a specific stone actually is? Call or text (940) 398-5589. If we don't know for certain, we'll say so and find out.