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Countertop Geology, Part Six. Let's talk about rocks some more!

September 9, 2014

This is round six of the Great Rocks Thread!

Please post your rock questions here. I've copied the basic info about quartzite and marble here because this is the most frequent question.

Quartzite and marble are hopelessly (deliberately?) mixed up in the decorative stone industry. My point, aside from just loving rocks, is to help folks learn how to tell the difference between the two so you are not at the mercy of a sales rep when a multi-thousand dollar purchase hangs in the balance.

Quartzite is much harder than marble and will not etch when exposed to acids. You can tell the difference between quartzite and marble by doing the scratch test and the etch test.

Scratch Test
Take a glass bottle or a glass tile with you when you go stone shopping. Find a rough, sharp edge of the stone. Drag the glass over the edge of the stone. Press pretty hard. Try to scratch the glass with the stone.

Quartzite will bite right into the glass and will leave a big scratch mark.
Any feldspar will do the same. (Granites are made mostly of feldspar)

Calcite and dolomite (that's what marble and limestone are made of) will not scratch. In fact you will be able to feel in your hand that the rock won't bite into the glass. It feels slippery, no matter how hard you press.

PS - don't press so hard that you risk breaking the glass in your hand. You shouldn't need to press that hard!

Etch Test
Etching is when the surface of a rock is dissolved from acids like lemon juice, vinegar, wine, etc. It is the primary bummer about using marble in a kitchen. Etching is most noticeable on polished rocks. Etching is not prevented by sealers, no matter what you hear from the sales rep!

Doing the etch test is simple: bring home a sample of the rock and put lemon juice or vinegar on it. Even after a few minutes the results are usually obvious. Etched areas look duller and are discolored compared to the rest of the slab.

Some people get conflicting results with these two tests, but normally anything in the marble family will not scratch glass and it will etch.

Quartzite and rocks in the granite family will scratch glass and will not etch.

Super White, the rock that started this whole discussion, turns out to have small amounts of quartz in it. Not enough to make the rock durable, but just enough to confound your test results because it can kinda sorta scratch glass. Real quartzite really gouges glass and even makes a grinding sound as it does so. But Super White can scratch glass somewhat, in some cases. So always do the etch test too because even with a little quartz in it, Super White will still etch.

For reference, here are links to the other rock threads, in which many types of rocks have been discussed.

Rocks 101: The Lowdown on Super White

Rocks 102: Marble, Quartzite and Other Rocks in the Kitchen

Rocks 103: Countertop Geology: Marble and quartzite and granite, oh my!

Rocks part 4, Marble, Granite, Quartzite

Rocks part 5, Marble, Quartzite, and other favorites

With that, let the rock conversations continue!

Comments (728)

  • simmtalker
    @speedlever Thank you for the water test idea!! When I go for the layout appointment, I will ask them to do that.
  • speedlever

    @simmtalker In our case, I was frankly shocked at how quickly the water soaked into the quartzite, even standing on edge so the water quickly ran off onto the floor. Other quartzite slabs we tested showed no sign of absorption. So be careful of the porosity issue. The slab in question for us was really sandstone, although the shop classified it as quartzite because of the hardness (as it readily gouged a glass tile).

  • boxerpal

    Hi Karin-Mt,

    I want to thank you for all your help over the years. I remember reading all about Virginia Jet Mist years ago and buying that counter with confidence.

    This time, my DH and I chose our counter with eyes wide open. Rio Venato Marble. I know friends tried to talk me out of it. But we love it and have accepted that it will get some damage. Our plan is to have the fabricator come out every 4 to 5 years to clean, polish and reseal them.

    I thought that maybe you could help me with a few questions. The Rio V is definitely a marble but appears harder than other marbles with our scratch test. It will definitely etch and will stain too (we know this!). Do you know anything about this stone? The fabricator is using a product called Dry-Treat StainProof. Have you heard of this?

    Our fabricator is recommending that we hone the counters. (Right now they are polished) He says this is going to hide the inevitable etching. He recommends this for all marble owners as they are happier with the results over time. What are your thoughts? I know honing will mute the colors and that is okay but will they still be able to seal them? They say no problem. They can't guarantee that a stain will not occur but they believe with Dry-Treat StainProof treated counters a stain will be easier to remove.

    One of the reasons we chose this marble is the movement and colors. There is enough color (browns, tans, beige, grays, gregies, blues, navy and even rust) that when a stain occurs it is going to blend better than some of the other marbles or pretend quartzites we fell in love with.

    We did a little research and were told this is from Italy. If you know of anything about this stone please share. Knowledge is power and can only help us to enjoy our beautiful piece of Mother Nature.


  • Gen H
    Boxerpal- that is gorgeous!
  • karin_mt

    Hi Boxer,

    Agree with Gen H, that is a truly beautiful stone. I know you've been wrestling with this decision, so that's great that you've found the answer! Going in with eyes wide open is the best way to go, and you have certainly armed yourself with knowledge (as well as self-knowledge!).

    I don't know that particular stone and when I googled it, not much came up. It's either not common or it goes by another name.

    Did you test the porosity and staining? Not all marbles are porous. See if you can get a sample to do that. Last week I did some tests on porosity by putting stones edge-wise in a shallow pan of water. Only the bottom inch of the stone was in the water. Then I watched to see if water wicked up into the stone. It was cool too see how different stones reacted.

    Honing will make etches less visible, yes.

    I hear that honing makes the surface of the stone slightly more susceptible to staining, but I haven't run any tests to check that out either way. For sure, a polished surface is easier to wipe clean. But I don't think it's true that polishing reduces the porosity of the stone. You can definitely seal a honed stone.

    I also think that honed marble is particularly beautiful. The stone naturally has a satiny luster and honing emphasizes that.

    I don't know anything about that particular sealer, sorry.

    Sorry I don't have definitive answers to your questions, but I agree you are on the right path. Good luck and keep us posted!

    - Karin

  • Gen H
    You are giving me countertop envy. I’m doing Navajo white quartzite. In my mind that stone is worth the risk and the patina might make it even prettier.
  • boxerpal

    Thank you Karin,

    That is a great idea to test the porosity of the stone. Brilliant! My installer/fabricator is actually testing to see if this marble stains worse than others. He and his crew actually test before they install. He did tell me this is a harder marble that the some of the others we were looking at. He has better access to the stone yard and those in control over there so can get samples. He actually went over after I picked our stone to look at the slabs himself to see if there was any issue with them. I will ask about porosity. And find out if I can do my own tests.

    Meanwhile here is what i have learned...And it is actually called Statuario Venato Rio is the short part of the name. I still hope to do my own testing.

    Thanks again Karin,


    Statuario Venato Marble is a kind of white marble quarried in Italy. This stone is especially good for Countertops, monuments, mosaic, exterior - interior wall and floor applications, fountains, pool and wall capping, stairs, window sills and other design projects. It also called Bianco Statuario Venato Marble,Statuario Venate Marble,Statuary Venato Marble,Statuary Vein Marble, Marmo Statuario Venato


    From Italy ( Cava n.103 Calocara B, Provincia di Massa Carrara, Tuscany

    Water Absorption:0.14 - 0.19 mass%

    Compressive Strength: 108.0 - 115.0 MPa

    Density:2665 kg/m3

    Flexural Strength: 11.0 MPa

    Petrographic definition: Marble

    Massa Unit Volume: 2665 kg/m3
    Water Absorption: 0.19%
    Breaking Load Compression Simple: 115 MPa

  • boxerpal

    Thank you Gen H... that is beautiful too. I think your countertop will be stunning.. What kind of edge are you doing? Backsplash? So beautiful.

  • karin_mt

    The water absorption numbers are promising. And yes, that name makes more sense!

    Marble, by definition, is always within a narrow range of hardness, from 3 to 3.5 on Mohs scale. But some people use 'hardness' to say that the stone is strong/durable, that it's not prone to chip or flake, or something like that. Technically, hardness is just a measure of how easy it is to scratch it. Either way, the info from your fabricator and their willingness to test the stone beforehand are good signs!

    Gen H, if that stone is quartzite it'd be a perfect replacement for Fantasy Brown. Visually, it's similar. And beautiful!

  • Gen H
    My backsplash is window or exposed brick. Karin thank you for sharing your knowledge. Happy 4th!
  • BruceFan9

    Hi Karin, I was looking at stones over the weekend and I came across leathered Blue Fusion which about knocked my socks off. They did not have a sample for me and there were no exposed edges. The wholesaler assured me it is "a true hard quartzite." They claim it did not etch in their lemon test overnight. The saleswoman also said it didn't stain, but I don't know what they tried to stain it with.

    I put a hold on two slabs and then emailed the fabricator. The fabricator called right away and warned me of two things: that she does not sell Fusion as a quartzite but as a dolomite, and that if it chips, it's white inside and difficult to nicely repair.

    It's very likely that I'll be scared off by the pricing anyway (no idea what I'm getting into there) but if not, is this stone a known problem? I have googled and I'm not finding complaints about it, but I don't want to baby my counters and if she's right about it being dolomite, I guess I'd have to. Any information would be so appreciated, thank you!

    Some photos... my color palette is blues and greens so this is just beyond beautiful to me.

  • BruceFan9

    And here it is with samples of Showplace's Hale Navy and Gunsmoke.

  • karin_mt

    Huh, as far as I know. Fusion is actual quartzite. But that one does look a little lighter and grey-er than most others I've seen. Can you visit the slabs in person and take a pocket knife to try to scratch the slab? Just ask to do it near the edge. Try it in each of the different colored areas.

  • Kate Zink

    Gen H that is beautiful stone! I am happy with my FB but now have stone envy LOL

  • BruceFan9

    Thank you, Karin. The fabricator hasn't even seen them in person; it seemed like it was a shop rule that they call any Fusion dolomite which seems strange unless they've been traumatized by a slab at some point.

    The slab shot that I took looks a bit lighter than it is. Here are the ones the warehouse saleswoman sent me--but they seem a little dark! I will have to go back anyway because the second slab was behind the first and they'll need to drag it out for me.

    I'd like to see them in good light, too.

    I wish they'd leave me alone for five minutes, but they don't let you just wander around (knife in hand, LOL).

    "Hello, I have come to stab the quartzite, please!"

    I'm trying not to get too attached to it because even if it's quartzite, the pricing may be too high. I've been looking at slabs for a year. Insane.

  • karin_mt

    I'm pretty sure that's the regular Fusion which is quartzite and is also very expensive. But still, you should definitely stab it, obviously. :)

  • Lisa 902

    Maybe it'll be less expensive because it doesn't have the riot of color that other Fusions display...

  • Lisa 902

    @boxerpal that is GORGEOUS, oh my

  • boxerpal

    @Lisa 902 thank you. We are in love with the rock.

    @BruceFan9, That is a beautiful stone, Hoping it is exactly what you want in a price you can afford.

  • m1

    Hi All. I'm new here, but have been reading along for awhile. One of the stones we've fallen in love with is a Victoria Falls quartzite. I can't find a lot of references to it, so we're a bit skeptical. Like so many of you, I can't get my hands on a sample for testing purposes. Karin, can you help us out? Anyone out there know about this stone? Thanks much!

  • karin_mt

    Going by eyeball, I think that one is similar to Taj Mahal, in that it's a 'crystalline quartzite.' That means it's been exposed to a high degree of metamorphism, to the point where it nearly melted. On stones like this, the things to watch out for are brittleness - which can make fabrication slow and tricky - and porosity along the little fracture lines. Although I have never heard anyone complain about that IRL.

    Can you do a scratch test on the surface of the slab with the tip of a pocketknife (or similar point metal object)? If it's real quartzite, you won't really be able to scratch it at all. If it's marble, you'd be able to scratch it easily. Most places will let you do that, near the edge of the slab.

  • m1

    Thanks, karin. The owner of the store selling the slabs says it actually is mined from the same mountain as Taj Mahal, so if that's true, it goes hand in hand with your explanation. It is a beautiful stone! I'm hoping there are some others out there who have installed it and can share their experience.

  • m1

    Karin, Based on your info about this being similar Taj Mahal, how do you think this would stand up for porosity and staining?

  • m1
    Thought I'd include a picture of the Victoria Falls!

  • truly16

    The look you're going for is very similar to what I did. Mine is Taj.

  • m1

    truly16---How pretty! Love the island! Still new, I see, but are you happy so far? Any stains, chips, cracks, etc.? Rec'd a comment on a different thread yesterday of a new install with a stain left by a wet box, of all things. Thanks for posting this great pic!

  • truly16

    Yes, it's still under construction. Our contractor walked away (looong story) so we are stuck right now with 60% done. In any case, I so far love it as much as I can use it. The countertop has not stained or cracked. I'm really glad I went with Taj Mahal.

  • paynerobin

    Karin, I there anything you can tell me about this granite slab? The stone yard says level 7 exotic leathered granite from Brazil. I can't find anything similar looking on the internet. What are the lighter semi translucent grayish patches that seem to have lines running through it?

  • Stephanie S
    This is a great thread, appreciate so much the time and effort of Karin! I am looking for a countertop for an outdoor kitchen area. The slab yard told me to avoid anything with feldspar. That seems odd to me. Any advice on what to look for when choosing a slab for outdoor applications?
  • karin_mt

    Stephanie, thanks! I'm glad the info is helpful. Avoiding feldspar makes no sense at all. Most granites will be fine outdoors, but they will fade over time. Everything will. I'd recommend testing for porosity, since rain/snow will allow moisture to sit on the countertop.

    This article shows how to do porosity tests at home.



    The patches in that granite are feldspar crystals. I do not know anything about this granite, but I'm not sure what would make it exotic or expensive. Looks pretty much like regular granite!

    Good luck to both of you!

  • PRO
    Joseph Corlett, LLC

    "Most granites will be fine outdoors, but they will fade over time."


    Is the stone fading or is it the resin in the stone that was applied at the factory that is failing from UV light degradation?

    I've seen some resinated exterior slabs in Las Vegas that looked like they were cooked. The built up edges were toast.

  • karin_mt

    It's both, Joe. The stones themselves fade - but in a benign way. The colors just become less intense. Good point about the resins, because those can turn dreadful colors, or dry out, or who knows what. That's a good thing to add to best practices for shopping for outdoor stone - look for something with minimal or no epoxy on the stone or on the edges. Get something as natural as possible.

    Does that make sense? To you?

  • PRO
  • kevingofron
    Hi, I went to a stoneyard looking for a granite slab for our basement bar. Found a great looking slab that had all the colors we were looking for. The label was torn in half, but from what I could make out, it looked like “Saturn”. The slab is leathered which is the look we want. Pic below. Any knowledge on this one that we should know? Really hoping it will work for our intended use.
  • kevingofron
    Hi, I went to a stoneyard looking for a granite slab for our basement bar. Found a great looking slab that had all the colors we were looking for. The label was torn in half, but from what I could make out, it looked like “Saturn”. The slab is leathered which is the look we want. Pic below. Any knowledge on this one that we should know? Really hoping it will work for our intended use.
  • ginny20

    Afraid I can't answer your question, but that is a beautiful slab. Hope it gets Karin's blessing.

  • karin_mt

    It might be Saturnia, which is a type of schist. You'll want to proceed with caution with that one because it can contain large flakes of mica, which can flake off and shed after fabrication. The edges can be problematic, too. But it depends how large the mica flakes are and how much mica there is compared to the rest of the rock. Have a really close look at the slab and be sure to talk with the fabricator about this one. I'd give it a 'yellow light' overall. Definitely worth pursuing, but carefully.

    Here's more about schist:


  • CC
    Hi Karin, I have white Macaubus in my bathroom. It was installed about a year or so ago. I now want to seal it again but what should I use to clean it first? I was thinking alcohol? Maybe acetone? I don't want to damage it. The reason I want to seal it again is there's a little darkening underneath the soap bottle. What do you think? Thanks, you are a wealth of information!
  • boxerpal


    My installer used DryTreat Stain Proof. You can get this on amazon. A few others here have chimed in that Miracle Sealants 511 Porous Plus is good too. I have not heard of the one you are using but I am sure you can research on Amazon.

    Maybe KarinMT will have some other suggestions.

  • karin_mt

    I actually don't know that much about the cleaning and sealing products, so I'm glad you chimed in, BoxerPal.

    But you are on the right track Carolyn, you definitely want to be proactive in sealing it, and yes, you want to clean it first and get the soap out. OldRyder and Joseph Corlett are seasoned fabricators that can give better advice than I can.

  • kevingofron
    Thanks Karin, it is Saturnia and the fabricator looked at the slab and told us that we need a simple edge due to rounds being an issue due to the mics. He wasn’t too worried about after install durability, was more concerned about the fabricating process. He said leathered by the stoneyard actually keeps the granite stronger versus polishing or honing at the fabricator when mica is involved. Any thoughts on that?
  • CC
    Thanks Boxerpal, I'll check out those sealers. I got Bulletproof because the fellow we bought the counters from said that's what they use. Thanks Karin, yeah, I don't want to put anything on it until I clean it first... I also have Silver Cloud Granite (honed) in the kitchen that was installed roughly the same time. I think I should seal this too because I've noticed rings that look like etch... is it even possible to etch Granite? Maybe because it's honed? Actually, I think it's Gneiss, right? Here's a pic...
    Honestly, they are very faint and I think a little scrubbing will get them out but I figure sealing these as well can't hurt, right? BTW, I love these counters, they are really nice... or is it Gneiss?
  • karin_mt

    Carolyn, that's a nice gneiss! It won't etch, so it's something else that's causing the rings. I'd get it clean, and then seal it. You've got two nice stones in your house - both of those are among my favorites.

    Kevin, a non-polished finish is a good idea. It's not that it's stronger, but it will look better.

    With a polished finish on schist, the mica edges tend to stick up conspicuously. I'm pretty sure the same thing happens with other finishes too, but it's less noticeable so it's not as much of a problem. But the stone can't be made smooth, so think about if that's something that would bother you or not.

    Fabrication may well be tricky because if there are distinct layers of mica, the stone can break there. But all stones are pretty solid once installed. Watch out for large mica areas near the edges, particularly if there is a band of mica that runs parallel to the edge and is unsupported from underneath.

  • boxerpal

    Carolyn, those counters are gorgeous! I am not sure either about the silver cloud rings but I am sure your installer might have ideas. Good luck and enjoy your stone.

  • govner

    Hi Karin, having issues with what is supposed to be mercury grey quartzite. Issue is that the quartzite keeps staining. Fabricator has sealed a couple times on-site (in our home) and stains still occur. Is this typical of quartzite or might we have some "bad" slabs? Installer says that issues like ours happen on occasion but we're not sure what to believe. Are there different densities of quartzite? Slabs passed the scratch tests. Thanks.

  • govner

    Me again. The first pic is olive oil. The second is water that penetrated the fissures after only 10 minutes.

  • PRO
    D Old Granite LLC

    govner , there is also a chance these slabs were treated with acid solution in the country of origin to remove any rust, and because of the acid wash it opened pores and now much more susceptible to staining; well, I recommend you or your stone fabricator looking with Stone Fabricators Alliance (they have a Facebook page) on how to treat your stone. Thank you,

  • karin_mt

    Hi Govner, sorry for my late reply. Yes, there are different porosities of quartzite, and it looks like your is somewhat porous. That's odd-looking that the stone is absorbing liquids along those scratches. Are those natural? Are they cracks, or scratches? Hard to tell from the photo.

    Either way, if the stone is staining even after being sealed a few times, that's a problem. Hopefully the fabricator can give you some advice. If it's happening just along the cracks, maybe some epoxy or filler might help.

    Sorry that happened and I hope you can get it resolved!

    More info on quartzite porosity: http://usenaturalstone.org/properties-of-quartzite/

  • tinhorn12

    We like Dolce Vita or La Dolce Vita, but have seen it marked Marble and Quartzite at different wholesalers. We will try the scratch test, but generally, is Dolce Vita appropriate for a large kitchen island?

  • HU-259104893


    My my husband and I love Namib Fantasy, and would like to use it for our kitchen counter tops; however, we are confused about whether the stone is quartzite or marble. One manufacturer says it’s marble, the other quartzite. It scratches glass, but not as deep as our current granite tile countertops. Are you familiar with this product? Pic included below

Need help with an existing Houzz order? Call 1-800-368-4268 (Mon-Sun).