THE PILANESBERG STORY
Described by geologists as the Pilanesberg Alkaline Ring Complex, the Pilanesberg is one of only 3 alkaline volcanoes in the world and is exceptionnally old. The formation of the Pilanesberg occured 2000 million years ago. At its zenith, the volcano towered to 7000 meters in height, rivalling even Africa's highest peak, Mount Kilimanjaro, in grandeur !
Over time, a series of volcanic eruptions occured. There were further outpourings of lava, craters collapsed, ring fracturing took place around the volcano and magma was squeezed into these fractures. The end result is several concentric "onion rings" of rocks of different ages.
Erosion over many millions of years has stripped away the mountain and the highest peak, Matlhorwe, now rises 700 meters above the valleys. What we see today then is not so much a volcanic crater, but a cross section through the magma pipes that were located at great depth below the mountain's summit.
A high number of rare minerals occur in the park. :
- volcanic tuff
- nepheline syenite
- kimberlite
- fluorite
- uranium-mineralized tuff
- several form of foyaite : green foyaite, red foyaite, white foyaite and 'ledig' foyaite.
(Extract from "Pilanesberg Nature Reserve - Map & Guide book")
RED FOYAITE :
Foyaite is a variety of nepheline syenite. It is a rare igneous rock. The term does not fit into the modern nomenclature of igneous rocks and therefore its use is not anymore recommended. The rock was named after Foya in Portugal. Originally the term was used as a synonym of nepheline syenite.
This earthcache will allow you to learn more about red foyaite.
ACCESS TO THE SITE :
The coordinates are bringing you to a official landmark from the Pilanesberg park ( G9 ) .
The landmark you are looking for is inside the Moloto picnic area.
It is a little off the main traffic in Pilanesberg Park. The track leading to the area is a little bumpy, especially during the rainy season, and it is necessary to favour hi-rider cars.
The good thing is that you can fully enjoy the landscape, Matlhorwe mountains and valleys without being disturbed too much.
Always keep in mind that you are in a wild game reserve, and that proper behaviour and respect to the animals is always necessary.
The inside of the picnic area is normally safe, but the presence of small animals such as snakes cannot be ruled out.
HOW TO CLAIM THIS EARTHCACHE ?
Send me answers to the following questions. Answers can be easily found on the plaque standing on the landmark, at the cache coordinates.
- Why is red foyaite colored red ?
- What are the 3 main constituent of red foyaite ? Can you identify them on the polished sample ?
- What is the shape of the polished sample you see below the board.
- (Optional, but always appreciated) : Take a picture of your own shadow on the nearby rocks. Take example of enclosed picture.
Send me the answers via geocaching message center.
I will contact you in case of troubles with the answers you provided.
Happy geocaching !