Does Granite Have Fissures & Cracks?

Sarabeth Asaff

There are many natural materials on the market today for use in home and building design. One of these products is granite, which can be found in tiles and countertop slabs. Like many natural materials, granite has some characteristics, which can concern homeowners.

Some types of granite may be prone to cracks known as fissures, understanding what these are and how they will affect your granite installation will help you make a more informed decision about materials in your home.

What Is a Fissure

Granite is an igneous rock, which means it was created from hot lava flow from a volcano. Fissures are thin, nonstructural cracks that occur during the formation process of the granite. When two separate streams of molten lava or magma intersect, they can leave behind a small separation between them. When the resulting stone cools and hardens, this separation is left behind as a small crack or fissure. Fissures are not defects and may not even go through the entire slab or tile of stone. If a fissure were to open, either during cutting, moving, installing or use of the stone, it can be repaired with epoxy.

Granites Prone to Fissures

The term "granite" describes a group of stones with a specific amount of quartz in their makeup. Some types of "granite" like Absolute Black, which is a classification of stone known as a gabbro, rarely develop fissures, because the material making up the stone is extremely dense. Some types of granite, however, containing the mineral serpentine are extremely prone to fissures. Pompeii granite, which has only the barest minimum of quartz to meet the commerical classification of granite, is extremely prone to fissures.

Looking for Fissures

If the look of fissures is a concern, or there are concerns about a weaker stone being potentially damaged during installation or use, inspect a potential slab for fissures before purchasing it. Inspect both the front and back of the stone. Look for thin, jagged cracks that are more than 2 to 3 inches in length. Run your hands over the polished surface of the granite, deep fissures can be felt while more shallow ones can be buffed away during the polishing process.

Filling Fissures

To many stone experts and lovers, the fissure is not a defect, but rather something to be embraced as the natural beauty of the product. However, if a fissure grows in size, penetrates through the stone to the other side or otherwise mars the durability of the stone, it can be filled. Use an epoxy based granite repair kit in a color that matches the mid-tones of the granite. Fill the fissure with the epoxy and scrape the surface smooth with a razor blade until the fissure lays flush with the rest of the surface.