The Mystery of Biotites

Granite is an igneous rock formed millions of years ago from volcanic lava flow. This is what gives granite its hardness and resistance to scratching, staining and heat. The colors and veining of individual slabs come from the various minerals found in the quarries where granite is mined.

Although there are many crystals and minerals in granite; it's main composition is quartz, feldspar and mica crystals. Mica Crystals, also known as biotites, are usually dark brown, green or black in color. These mica crystals are softer than the quartz or feldspar. When granite slabs are polished, the top layer of these softer mica or biotite crystals flakes off and forms small indentations or depressions (sometimes referred to as "pitting") in the stone. These depressions are not considered flaws since biotites are simply part of the natural composition of all igneous rocks such as granite.

One way to tell granite from the polyester plastics or other manufactured counter-tops is the presence of these depressions. Some stones such as Baltic Brown or Dakota Mahogany actually have rather large depressions and a resin has been manufactured that can be applied to these granite slabs prior to their fabrication. However, even after this resin is applied one will notice the tinier depressions or "pitting" in these slabs as smaller areas cannot be hidden or covered up by this resin.

Remember that granite is a natural stone, just like the ones we find in our garden and on rocky beaches. Biotite depressions are not flaws in the granite; rather they are part of the beauty of this stone. Through the modern technology of granite quarrying and fabrication we are now able to decorate our homes with this natural wonder. And as each granite slab is unique, we also have a truly individual work of art to enjoy for years to come.

By Ann-Marie Rosavage, Ph.D.