Lonely Castle Koppie EarthCache
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This delightful park is only open periodically. But the exposed koppie (or tor) is well worth the visit. The cache is outside the park, and therefore available at all times. But try come when you can clamber around.
Lonehill Koppie Reserve is a very scenic little reserve to take the dogs on weekends. The entrance to the Koppies is only open on weekends from 01. September to 30. April. In case the gate, which is just next to the lake, is locked, the cell number of the security is provided on a placard at this entrance. The co-ordinates for the Earthcache take you outside the fenced area, so you can do this when the reserve is clsed. But I urge you to try and do it when it is open. There is an added advantage of having another cache located up the koppie (GCYJZ4 – Lonehill Koppie by cache-fan). However there is a safe parking area with stroller and toddler friendly play park at the co-ordinates for this Earthcache too.
This koppie (Lonehill) represents one of the most prominent of a number of Archaean granite tors (also commonly called “castle koppies”) developed in the central and south-western parts of the 3200 million year old Johannesburg granite dome. The dome stretches from Buccleuch and Halfway House in the east through Witkoppen and Honeydew in the west. The tors in this part of Joburg vary in both composition and texture. But generally consist of medium to coarse grained homogenous granodiorites and adamellites, as well as banded gneisses and migmatites. In some of the tors the granitic rocks contain large feldspar crystals (this is clearly visible in some of the rocks scattered around the park near the co ords) in a finer grained matrix – these are reffered to as porphyritic granites. Tors similar to Lonehill are extensively developed in the Archaean granites of Zimbabwe (think of the balancing rocks of the Matopos where Cecil John Rhodes is buried and other outcrops around Harare), Mpumalanga and Swaziland; and formed mainly by differential weathering of the faulted, fractured and jointed granites.
(Acknowledgments: guidebook to Sites of Geological & Mining Interest on the Central Witwatersrand.; Geological Society of South Africa; 1986).
In order to qualify to log this cache, you need to answer the following questions and s=email the cache owner. Any logs not accompanied by an email will be deleted.
1) Take a photo of you and your GPSr at this spot with the granite outcrop visible and include in your log. [Optional]
2) Look at the exposed granite (try find a “fresh” exposure on one of the rocks around – or if you planned your trip on an open day – some of the primary tor). Describe from the “crystal” or grain size whether this rock cooled quickly (like a dolomite or obsidian with small grains) or more slowly to produce larger grains.
3) Describe what the granite looks like (including texture and colours).
4) Explain how the rocks may have ended up “balancing” on each other.
Additional Hints
(Decrypt)
Erzrzore gb fraq lbhe rznvy! V hetr lbh gb gel naq trg urer jura gur erfreir vf bcra. Trg hc pybfr naq crefbany jvgu gur xbccvr – vg vf ERNYYL jbegujuvyr.