Is it a Crack or a Fissure on my Stone Countertop

Frederick M. Hueston

You wake up one morning and go into your kitchen to pour a cup of coffee and you notice a long pattern on your granite countertop that looks like it cracked.  You run your finger across it and wonder if it was always there or just occurred overnight.  Later that morning you call the fabricator who installed it, send him a picture and he says its just a natural fissure.  You have your doubts and wonder if there is way to tell the difference between a fissure and a crack. The following should help you decide if your granite, marble or quartz is cracked or if it’s a natural fissure.

First, almost all-natural stone has some degree of fissuring or veining.  In layman’s terms fissures and veins are inherent elongated openings in stone resulting from geological formation, environmental impact, mineralogical crystallization, and other factors.  They are sometimes referred to as “hairline cracks.”  The even smaller micro-fissure is only detectable through a microscope.

Fissures or veins usually have minimal unevenness, chipping, separation, movement, and fracturing.  Field measurement of a fissure’s width is difficult and prone to error.  A slight break in the reflection, an indentation and a less reflective finish are three factors that mostly indicate the presence of a fissure.

On the other hand, cracks are quite different than fissures and its indicators are readily apparent.  Cracks usually have noticeable unevenness, chipping, separation, movement, fracturing, and obviously broken pieces of stone.  With stress carefully placed on the area in question, movement leading to additional chipping and fracturing may be evident.  Also, noticeable separation allows an accurate measurement of the width.   Cracks are generally caused by mishandling or from improper support.

How to tell the difference

One test to perform is to see if your fingernail catches across the crack.  Gently run your fingernail across the vein/crack. A natural fissure and a vein will not catch. If your fingernail catches it is most likely a crack.

Another indication that it is a crack is to see if the suspected crack runs through or around individual crystals in the stone. If it run across and crystal it is most likely a crack. If it runs around the crystal it can be a fissure.

Of course, there are exceptions to these rules and if in doubt consult a an expert who can do an evaluation to be sure.