Monthly Archives: November 2014

Stun Marks in Natural Stone

Natural stones like marble and granite are just that – completely natural. They are cut from the earth, and formed into slabs or tiles for countertop, floor, and wall use in and around homes. Sometimes during the forming of these stones into slabs or tiles, or after the installation and during normal use, small blemishes may become apparent on the stone. Appearing like scratch marks or white circular “bruises” on the stone, these marks cannot be felt to the touch, nor can they be polished or ground away.


Known as stun marks, these bruises present a serious problem for some homeowners and consumers. Stun marks are created by a sudden hard application of force against the stone, which creates a cascading affect beneath the surface, causing the minerals and crystals to fracture. This shows up as a white mark in the shape of the impact.

Because stun marks go down deep into the stone, it’s difficult to get them out. They can be cut and dug out, and the area filled with an epoxy, but unless the color match is perfect, this solution is often more obvious than the problem itself.

Most homeowners only come to experience stun marks after installation. High heeled shoes, for example, are well known for stunning some types of marble.

Other times, some types of stone such as Calacatta or Bianco Carrara will arrive from the quarry filled with stuns caused when the stone was dug up. In these cases, it’s best for homeowners to be made aware of the presence of the stuns when they are viewing and selecting their slab or tile. Because stun marks are natural and part of the nature of stone, they shouldn’t be viewed as a “defect” in the stone, but merely as part of the natural beauty and variation that all stone can have.

The Most Common Natural Stone Problems

As natural stone continues to grow in popularity for several applications in and around the house, consumers are also beginning to notice some of the common problems that can occur. Understanding what these issues are is the first step to helping to prevent them.

Loss of shine on a polished stone is one of the biggest complaints by homeowners. This loss of shine can be due to etching, or the removal of some of the fine particles of stone on its surface. Etching can occur when acids such as vinegar or lemon juice come in contact with the stone. Homeowners that clean their counters with Windex or vinegar may notice a distinct loss of shine.

Loss of shine can also occur over time in high traffic areas as the stone is continuously scratched by shoes, sand, salt, and other particulates. To restore the shine, the stone needs to be reground and buffed by a stone refinisher.

Staining is one of the other most common problems noted with natural stone floors and counters. Because many stones are porous, they can absorb oils and liquids which can stain the stone. Regular use of impregnating sealers can help to impede staining, as can wiping up spills as soon as they are seen. Once a stain has occurred, it may be removed or partially removed with the use of a poultice.

Spalling is a condition that often occurs with slate, quartzite, and green marbles containing serpentine. With slate and quartzite, this condition is temporary and consists of small pieces of the stone flaking off the surface. The stones may be very dust or sandy for up to three months after installation.

Stone vs. Quartz Countertops

Homeowners selecting a new countertop have more options today than ever before. Among those selections is to use a natural stone counter, or a “man made” stone counter or quartz counter. There are several different manufacturers for quartz countertops, although most of them are made similarly. Homeowners deciding between the two types of material may not realize what their similarities and differences are, which could lead them to make the wrong decision for their home.

Natural stone counters can be granite, marble, limestone, slate, or a variety of other stones including dolomites and gabbros. Each type of stone can be slightly different from the others, with some requiring more care and sealing to help protect them, while others require little to no care.


The vast majority of natural stone counters do need to be sealed on a semi-regular basis, and should be cleaned with a PH neutral cleanser to avoid etching. Because these stones are completely natural, their color may vary dramatically from piece to piece and even within one piece. Sometimes pits and fissures may be found in the stone, as well as unusual minerals that could give the stone spots of unusual color or veining.


Quartz counters contain roughly 90% natural quartz, a mineral found in many natural stone counters. This quartz is mixed with a variety of resins and pigments, however, which renders the quartz counter non porous, stain resistant, and scratch resistant. These counters never require sealing, and do not have natural fissures or pits.


They also do not have any natural color variation; while there can be some slightly variation due to dye lots, these counters are usually fairly similar in one color from piece to piece and within one piece. Some may have veins or color flecks, but these are carefully controlled so as not to introduce random colors or movement into the counter.

For those that want a controlled and low-maintenance countertop, quartz counters can be a good option. For those wanting the color, movement, and variability that only natural stone can bring, however, nothing but stone can do.

Understanding Stone Classifications

Nearly all stones from marble to granite are given a classification of one type or another. This could be a letter grade or a usage recommendation, and these classifications can vary from one manufacturer or stone yard to another. Understanding what some of the more commonly used systems mean can help homeowners choose the right stone for the right application.


Most stones are graded at the quarry for their color, clarity, and strength. Stones that are consistent in color with few inclusions, fissures, or pits are usually graded with an A. These stones are often denser and more durable than others marked B through D. Stones that are graded at the other end of the spectrum as a D are usually more varied in color, with noticeable fissures, pits, or inclusions. A stone graded A is much less likely to break or crack than a stone graded D. Stones with grades in between these two may have any mixture of veining, color variation, and small fissures or pits.

Some stones may also be graded as residential or commercial. This can be misleading because each of those groups could mean one of two things. If the rating refers to color and veining, residential stones are the nicer, more evenly toned selections. If the rating refers to strength, however, then the commercial stones are the more durable, with residential stones being further broken down into light and heavy residential use.


Many stones are also graded just for color, with common classifications being:

  • Select, which means the stone that is homogeneous, with light color, and few veins
  • Standard, which means the stone is homogeneous, with normal veins
  • Classico, which means the stone is not homogeneous (spots, shadows…), and more veined

Stones that are graded standard or classico may also be graded A or commercial for strength, which further makes the issue confusing. Homeowners should determine what it is they want from their stone, so they can make the correct decision of strength or color to get the right material for them.


Granite Countertop Maintenance

Despite the recent wave of new materials making their way into kitchens across the country, granite remains one of the more popular options in kitchen counters. New trends in kitchen design are focusing on natural materials, and a new wave of homeowners is looking at granite – particularly with a honed finish – to complete their designs.


Unfortunately, there is a lot of misconceptions and misinformation amongst homeowners who are choosing granite as well. Many of these stones are not actual granite – the igneous rock made of silica, mica, quartz, and feldspar – but are actually commercial granites, or stones sold as granite. This group of stones includes quartzites, dolomites, and gabbros, all of which have specific maintenance needs.

Many homeowners may not realize that these stones need special care and maintenance to keep them looking their best. This is especially true of homeowners purchasing honed stones, as one misconception is that honed stone requires less care than polished.


Granite and natural stone maintenance is not difficult, and any homeowner can take it on, provided they understand what’s involved.

Upon selecting the stone, the water and lemon test should be performed on a sample to determine how much care the stone needs. A small amount of water and lemon juice should be put on the stone for roughly 10 minutes, and then wiped away. If the stone has changed appearance, then it is susceptible to these materials and needs extra care.

All stones should be washed with a PH neutral cleanser containing no acids or alkalines, and all spills should be wiped up as soon as they are seen to avoid staining, particularly in porous stones that darken on contact with water.


For porous stones and those that etch on contact with acids, an impregnating sealer should be applied on a regular basis. Water should bead up off of the surface of a well sealed stone; when it stops beading, it’s time to reseal the stone.

While not every stone will require this degree of care, many do. Knowing how to take care of them properly will help homeowners enjoy their new stone for years to come.