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Slippery rOck Gazette OctOber 2020|5
Training & Education
Is that Marble or Quartzite?
How to identify what you’re selling and installing
INrecent years, there have been com- plaints from consumers who purchase countertops from stone distributors who tell them the mate- rial is quartzite, which will not etch (a dullness of the surface) or scratch. Later, when their tops are etched and scratched, they learn the hard way that their tops are actually marble. This article explains the differ- ence between quartzite and marble so that consumers can tell what countertop
material they truly have.
About Marble
Marble is a metamorphic material that contains an abundance of the mineral calcium carbonate, which is soft and chemically re- acts to acidic substances. This means marble is very susceptible to acid etch damage. Heat, pressure, and other geological forces destroy or modify the tex- ture and structure of lime- stone or dolomite rock, resulting in a new form of rock known as marble. When the limestone or do- lomite are very pure, the resulting marble is white. When the quartz is mixed with iron oxide or other minerals, the resulting quartzite may have streaks, lenses (transparent pieces), and varieties color.
About Quartzites
Quartzites is also a met- amorphic rock, but dif- fers from marble in that it does not contain calcium carbonate. This means it is not susceptible to acid etch damage. Quartzite is formed when heat, pres- sure, and other geological forces destroy or modify the texture and structure of quartz sandstone. When the quartz sandstone is very pure, the resulting quartzite is white or gray. When the quartz is mixed with iron
Frederick M. Hueston
Stone Forensics
oxide or other minerals, the resulting quartzite may have streaks, lenses, and varieties color.
Simple Tests to Determine Stone Type: Is it Marble or Quartzite? Marble and quartzite can be very similar in appear- ance. Fortunately, there are a couple of simple tests one can perform to tell the difference between marble and quartzite: the scratch test and the acid test. If you attempt to perform either of these potentially destruc- tive tests, you should obtain a sample or use a piece of scrap countertop material to perform the tests. If neither are available to you, test in an inconspicuous spot knowing that the test may
cause damage.
The Scratch Test
In order to understand how the scratch test works, we need to provide a little more science. The hardness of minerals can be deter- mined by what is called the Mohs scale of mineral hardness. This scale rates minerals from the softest mineral, being a one, to the hardest mineral, being a ten. Calcium has a Mohs hardness of three. Quartz has a hardness of seven. A standard kitchen knife has a hardness of about six.
Use a knife to scratch the surface of a counter- top. The outcome indi- cates the hardness of the
mineral. If the knife leaves a scratch, the stone is likely marble. If there are no scratches, the stone is likely a much harder stone like quartzite or granite.
The Acid Test
Calcium reacts to acids, causing etch damage. The etch may or may not have texture, depending on the severity of etch damage. Common acids will not affect quartz. Vinegar or a lemon wedge can be used for the test. Place the lemon wedge or a drop or two of vinegar on the stone and allow several minutes dwell time. Wipe up the excess. If it leaves a dull spot, that a positive indi- cation for the presences of calcium, which indicates the countertop is marble and not quartzite.
Uh-Oh, It’s Marble
If you discovered you have marble, not quartzite, by way of these tests or be- cause you already installed countertops that now have etch marks or scratches, rest assured that you are not doomed to replace the countertops. There are methods available to professional stone resto- ration contractors to hone and polish countertops, virtually erasing damage and leaving the tops with a beautiful, pristine finish. To help them stay pristine, you can also make recom- mendations for care and protection appropriate for the countertop material.
It is unfortunate that marbles are being sold as quartzites. While they can look similar, they do not react the same. If you are in the market for new countertops, these tests can help you make an in- formed decision on your investment.
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Photo and design by Ellen Taylor Interiors + Design. | Fabricated by Stone Interiors Columbia.
BB Industries Announces Early Release of 2021 Automated Tooling Catalog
Based on significant enhancements to its automated tooling product offering and the addition of several key employees, BB Industries is releasing a dedicated 2021 automated tool- ing catalog. The cata- log, to be released in fall 2020, includes new vendors Apexx, Flexijet and Coldspring, joining valued partner vendors Alpha, BVC, Diamut and IMS. New products in- clude tooling for 5-axis saws, CNC routers, and inline polishers.
In addition to hiring many new experienced sales consultants from Diamut, Lackmond, GranQuartz, and Granite
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For over 26 years BB Industries’ philosophy has been to offer ex- ceptional products and first-class service to its partners in the stone, tile and concrete industries.
For more information, visit www.bbindustriesllc. com or www.facebook. com/bbindustries.