Join me on a journey into the very distant past, when our planet was about a quarter of the age it is today. We are deep below the surface, in the rock mix of volcanoes, mountains and sediments that have been pushed together as the first continent takes shape. We are kilometres below the surface, yet slowly ascending from way below us are huge masses of liquid rock, kilometres wide and deep. This boiling liquid rock is made up of several minerals, mainly quartz, feldspar and mica. They are all liquid. Slowly, like a vast blob of oil coming up through water, the mass makes its way closer to the surface, eventually slowing and cooling, kilometres below ground. The cooling takes literally millions of years, giving time for large crystals of quartz, feldspar and mica, evenly dispersed in the mix, to grow and solidify into granite rock.
This huge mass, along with many other such masses, has effectively welded together the rock it travelled through, forming a stable continental crust.
Over the vast lengths of time since its formation, the whole continental mass has been uplifted several times, and the surface above the welded mass eroded away, exposing what we call the basement rock – the ‘foundation’. Under the Lowveld, and indeed below Southern Africa as a whole, most of our ancient foundation is granite.
World-wide, granite is one of the best known rock types. At its most basic, it is made of three minerals – quartz, feldspar and mica. It’s very hard and resistant to weathering, making it ideal for countertops, gravestones and long-lasting architecture. You may well have some in your home. When you next see a piece of granite, have a look for the three main minerals – clear quartz, creamy/pink feldspar and dark mica.
Granite spotting in the Lowveld.
Pretoriuskop in the Kruger National Park is a great place to see a granite landscape, and you’ll see massive rounded domes of granite there. Closer to Hoedspruit, the ‘koppies’ on the way to Phalaborwa are beautiful examples of smaller more weathered granite landscapes. If you want to touch raw granite, there’s a great example on the R526 between Mica and Leopard’s Rock.
Further afield, the Matobo Hills in Zimbabwe is one of the most extensive granite landscapes in the world, and well worth a visit.
For some people, granite almost has a gravity about it. The huge pieces of ancient rock feel safe to stand on, they invite exploration; they offer endless beauty in the living communities growing on them, and the way light catches them at different times of day.
John has a continuous curiosity and an abiding passion for sharing the stories of South Africa’s remarkable biodiversity, rocks and landscapes. Based in KZN, he offers geological learning adventures throughout South Africa. Check out www.johnroff.co.za.
