Is my countertop quartzite, marble, or limestone?
See that sub-title ‘Is my countertop quartzite, marble or limestone?’ on top? Did you find it odd to see quartzite in the mix? If you read Part 3 of this series, you would know that quartzite has nothing to do with marble. But there are instances where I have seen factories, slab yards, and fabricators classify marbles or limestones as quartzites. Yikes!
If you have not read my post ‘Countertop Talks Part 1’ yet, I highly recommend reading it first to get familiar with the names of some of the stone types we will touch on in this article. Either way, knowing how the different stones form in nature helps us understand their properties, similarities, and differences and appreciate the forces of nature a little more.
The Origin of Rocks
If you missed my earlier post ‘Countertop Talks Part 2 - Glorious Granite and the Likes’ or just need a refresher on the origins of rocks, here it is.
On a very high level, there are three types of stones or rocks namely Igneous rocks, Sedimentary rocks, and Metamorphic rocks.
Igneous rocks are formed from cooled magma either on land or in underwater magma chambers under extreme conditions of heat and pressure.
Sedimentary rocks on the other hand form through the process of sedimentation which involves the deposition and compacting of sand, clay, and other minerals over time. This process can happen on land, meaning on beaches, deserts, or even on rivers and ocean floors.
Finally, we have Metamorphic rocks which as the name suggests form through the metamorphosis of stone! This process of metamorphosis takes millions of years in some cases and occurs under extreme environments of temperature and pressure.
If you would like to geek out and learn a little more about these different types of rocks, here is an article written by a Geologist: Geology of Natural Stone
How does marble form?
Now that you have a little background on what the different stone types are, let us dive into the origins of marble and what might be the reason behind these common classification misnomers.
Limestone is a sedimentary rock formed by the sedimentation, compression, and solidification of shells, fossils, corals, plankton, and/or lime mud in shallow, warm waters. The trademark of limestone is the presence of shells, fossils, and other organisms in entirety or fragments – all of which are composed of Calcite or Calcium Carbonate. Like all stones, the heat and pressure that different limestones are subjected to during formation vary which in turn affects their properties including porosity.
Given that limestone is formed by sedimentation and compression in shallow waters, and under less strenuous conditions of heat and pressure unlike granite and quartzite, the minerals in the stone are not as strongly bound making it less hard, more porous, and easily prone to scratching and etching by common kitchen acids like lemon juice, tomato juice, and wine.
Due to the nature of limestone, they are best used as tiles or wall coverings rather than as kitchen countertops unless you are willing to be diligent about sealing it regularly and being gentle and clean in daily usage. Personally, I am a very messy cook and would not dream of putting this stone anywhere around the kitchen. However, limestone is easy to work with and has a very soothing, unfirm look which makes it a great choice for building stone. Need proof? Check out the Empire State Building or the Pyramid of Giza.
Now, when the limestone beds get buried under continents and are subjected to increasing heat and pressure, the calcite fuses together tightly giving marble its trademark white color.
What type of rock is marble?
Marble is a metamorphic rock formed through the metamorphosis of limestone. The white color of the marble comes from the fused calcite crystals whereas the colors in the marble come from the clay, iron, or other minerals that got trapped in the stone during the metamorphosis.
The fusion of calcite crystals during the process of metamorphosis makes marble harder, and less porous in comparison to limestone. However, the main mineral in marble remains Calcite or Calcium carbonate which is still susceptible to common acids in the kitchen and is more porous compared to stones like granite and quartzite.
Irrespective of these shortcomings, marble still has the old-world charm and elegance that cannot be replicated with any other natural stone and much less with a manufactured product. It is very commonly used as flooring, building stone for interior and exterior applications, in kitchens as countertops, and backsplashes, and as vanity tops to name a few. Just like limestone, marble performs exceptionally well when used as building stone which is showcased by the world-famous Taj Mahal.
So, how can marble be classified as quartzite?
Truth – it cannot be classified or at least it should not be. They have nothing in common. However, there is a small number of limestones or marbles which contain another mineral Magnesium, and are referred to as Dolomites.
Dolomites are made of Calcium Magnesium Carbonate versus just the Calcium Carbonate that limestones and marbles are made of. The presence of Magnesium in Dolomite makes it a little harder and slightly less sensitive to acids in the kitchen which means that it does not etch immediately like marble and limestone would. Do you see where it begins to show the qualities of being a quartzite?
Well, those are the properties that prompt some factories, slab yards, and fabricators to classify these dolomites as quartzites which in my humble opinion should not be done. I have also seen dolomites marked as marbles, dolomitic marbles, or dolomites, all of which are more appropriate representations of what the stone is actually made of.
Have more countertop questions or cannot decide which one to get? Hit me up! I love talking about them. :)
Check out my other posts on the origins of different stones like Part 2 about Granite, Part 3 about Quartzite, Part 5 on Travertine, Part 6 on Onyx, or Part 7 on Soapstone, and subscribe to my Newsletter at the bottom of the page to be notified when new posts are published. You can also follow On my Lanai on Pinterest and Instagram to be notified of new posts.
Comments