Natural Stone Tile Information Resource

Natural stone tiles are produced from natural materials that have been quarried then cut into slabs, given a finished, and afterwards cut into different sizes as tiles or smaller slabs used as solid installations.  Common types of stone used for tile include granite, limestone, marble, slate, and travertine.  Within natural stone are many different characteristics that depend on where and when the stone was quarried.  Also the minerals, metals, temperatures, time, etc connected with the sediments which was the source material of the newer stone will determine those features.

Limestone is a stone that is formed over millions of years primarily from calcium remains from standing bodies of water.  Compacted remains become the limestone.  This process takes millions of years.  The layers of sedimentary deposits pile up under tremendous pressure.  Limestone is typically found with a smooth honed surface, some pitting, and if you're really lucky ... fossils or maybe some sea shells.  The materials found differ based on the specific deposits of the site.

Granite is composed of feldspar, mica, quartz, and what has come to called "hornblende".  What exactly is in the hornblende or mix of materials can be very different.   It is that variation of materials that gives granite its variety of colors and textures.  Granite is typically one of the most consistently textured natural stones.  Another features of granite stone is a crystalline structure and is considered the hardest of all natural stones. Granites qualities are resistant's to acid etching or scratching.  Also fire and heat resistant.  There are three finishes Flamed, Honed, Polished. Granite is virtually indestructible and so a good investment for your home.

Marble is made of limestone that has been crushed under super heated  incredible pressure creating crystallization.  This produces a denser and so heavier and harder stone capable of being polish.  Like most natural stones different minerals creep inside creating the many different colors and the character of the stone.  Marble is most has the appearance of grains of crystals running within veins that travel through the marble.  These can vary widely from stone to stone. It's hardness makes marble durable.  To keep marble looking it finest a regular maintenance schedule has to exist.

Travertine is primarily heated limestone pushed up to the earth's crust by water under hydraulic pressure.  Places where travertine is commonly found are mineral springs, hot springs, geysers and caves are good locations to find travertine stone. In these areas carbonate- water is exposed to the air.  After the water evaporates what's left behind are small deposits or layers of calcium carbonate.  Also referred to as banding.  Travertine has a layered appearance for this reason. Another of it's many characteristics are (usually) smaller holes distributed throughout the stone.  These are caused by water activity during the production of the stone.  These holes or (Pukas) may be filled at the factory or left unfilled.  These holes can be filled or left as is.  The type of application the travertine will be used for will have a lot to do with this decision.  The holes can be filled with cement or resin. Do not use resin for outside applications it will fade in time and create a discolored look. Use a colored cement instead.  Travertine typically has earth tones that stand out from a lighter tan background.

Also can be known as arenite. This is a clastic sedimentary rock. Mainly sand-sized minerals and rock grains deposited layer by layer compacted or cemented together over significant periods of time. The consolidation and compaction of sand is held together by a natural cement like clay, silica, calcium carbonate, dolomite, iron oxides, lime, etc. Most sandstone is composed of quartz and or feldspar and is gritty to the touch. The hardness will vary from soft to hard depending on the clast and cement composition. The color can be grayish, yellowish, reddish, or whitish. The variation in minerals that make up the stone and the cement types present will determine the colors.  Brown, red, purple, and pink sandstones are known by the name brownstone.  Sand stone is very porous and water will penetrate it easily. Water can peel off layers and freezing temperatures will cause the stone layer to split off in pieces. These reactions will also affect the grout joints causing deterioration. Sandstone weathers best when its end grain faces exposure to the elements.

A fine grained smooth stone that is created from materials like mud stone, shale, clay, or volcanic ash under pressure and cool temperatures for millions of years.  Through geological tectonic compression minerals within the slate like basalt, clay, chlorite, mica, or quartz go through a process called foliation.  A re-alignment of minerals forced to shift from pressure in another direction other than the slate was originally laid down.  These forces change the fundamental structural.  This characteristic is known as "Slaty Cleavage" or "Fissile". The result can appear as a banding or striation effect with different minerals being separated by availability and time being represented by colors and or textures.  While slate's more common characteristic color is grayish blue a wide variety of color do exist.  Much about the colors depends on the organic materials present in the rock.  Chlorite turns slate green and iron oxide creates a reddish purple tone.  Surface texture and luster can differ greatly as well.  Slate can have a dull matte or a shiny finish.

Common Stone Issues, Deterioration, and Erosion

  1. Acid Etching
    An erosion like process that causes an etching effect of the stone surface due to exposure to a variety of acids.  Just about anything can be the cause.  Acidic foods, acidic stone cleaners even acid rain will cause etching.
  2. Chipping
    Chips can be smaller or larger pieces. More often seen at the corners or edges of the stone due to stress factors.  A common reason for this stress is re-pointing stone done with the wrong kind of mortar, or way too much mortar stuffed into the joints.  Repairs of chipped stone should be done by a stone contractor.  For the repairs to look right you need a skilled professional.  Sometimes the chips can be put back into place.  Other times other cosmetic procedures can be applied to restore as natural a look as possible.
  3. Cracking
    Flaws or narrow fissures within the stone are sometimes the cause.  Structural stresses due to the processes of settlement or structural problems also can crack stone.  Accelerated oxidation can also be the cause.  Just looking at the cracks themselves can tell you a lot about why the stone cracked there at that exact spot.  Look for the signs of what it could be.  As mentioned before moisture, water, metals, other chemicals can all affect the integrity of the stone and cause cracking which can be dangerous depending on what that stone is doing or it's function.  Consultations and repairs should be done by a skilled contractors who can either patch the crack or replace the stone if possible.  For safety reason it is especially important to hire a licensed stone contractor if the stone is part of or an entire support structure.
  4. Crumbling
    This can happen due to inherent flaws in the stone, oxidation due to internal or external factors, or deicing salts.  In large or supporting stones this can cause a serious problem. The best way to prevent this is to maintain your stone material properly and keep away anything harmful.  Once the damage has happened there is really nothing natural you can do to fix it.  When dealing with solely cosmetic issues or surface crumbling you can try to restore the surface using a variety of methods and products which depend on the stone type and it's condition, but it will be a more of a repair than a restoration.  Deep with the stone there is currently nothing that can be done for the stone.

  5. Discoloration or Stain Types
  1. Bronze or Copper Metallic Stains
    There are two common metallic stains copper and iron.  The source can be within the material itself or come from an outside source.  Staining from bronze and copper sources either internal or from water run offs will range from a green to brown colors.   The staining is a result of the dissolved copper salts either from bronze or copper which find their way into the stone and then oxidize.   The staining will be in streaks that follow the run off water's course.
  2. Grease or Oil
    Organic or inorganic oils will penetrate stone almost immediately.  How deep into the stone will depend on a few different elements.  The viscosity or how thick the grease or oil is will matter.  Thinner grease or oil is worse. It works it way into smaller holes and deeper into the stone.  The temperature of the stone and of the oil will mater. In both cases the warmer they are the worse it is.  The material in the stone will expand more if the stone is warm. If the oil is hot it will warm the area that it is absorbed by and penetrate more so as well.  How porous the stone is and what type of finish will matter.  A high polish finish would fend better than a rough textured stone finish.  Grease and oil stains will often appear as a darkening at the area of absorption.
  3. Organic
    Organic matter can also stain stone.  Especially stone outside.  Decomposing organic matter like bird droppings, bugs, pet urine, pet poop, etc. All of these can stain your stone.  This type of staining will usually appear as a darkening of the stone's color.  Outside stone can sometimes recover on it's own with UV exposure from the sun the stains often dissipate on their own.
  4. Rust
    Rust stains are probably the most familiar of all to us.  We see them often.  The reason for this is the common use of iron in everything we build as well as the presence of iron within the materials themselves.  The most common of all are the surface rust stains.  The second kind are from iron often used as a structural element.  With direct contact to iron, common moisture or water will penetrate the stone and either introduce the iron or activate iron oxidation within the stone by coming in contact with the iron within it.
  • Efflorescence
    This will appear as a caulky white or dark colored film on the exposed surface of stone.  It is caused by moisture or water carrying mineral salts from the ground upward and into the stone.  On occasion you will see this effect even on un-glazed porcelain tile.  In this case the impurities within the bisque cause the similar effect.

  • Erosion
    Erosion can be the result of general weathering as explained below or it can be specifically due to something that comes in contact with the stone on a regular basis.  Often equipment like lawn mowers, weed whackers and the like can cause deterioration from consistent abuse or regular neglect.  Limestone, marble, onyx, and travertine are especially susceptible.
  • Filled Holes
    Porous stone slabs or tiles will often come with holes filled with resin or cement.  With exterior applications exposure to UV rays from the sun can change the color of resin.  If stone must be filled for exterior applications go with cement filled as an alternative.
  • Weathering
    The most common effect of weathering and erosion is loss of precise detail.  More degrading effects can occur on the appearance and structural soundness due to rain, ice, snow, extreme changes in temperature, wind and other pollutants.  A combination of one or more of these can occur at the same time. When rain combines with atmospheric gases acid rain can be the result.  This can cause a loss of the stone's integrity.

    The information contained in this document represents the current view of Duval Tile & Stone on the issues discussed as of the date of publication.

    This White Paper is for informational purposes only.