Gneiss (pronounced nice) is a coarse grained metamorphic rock. Heat as well as pressure is involved in its formation and this is the most metamorphic rock known. Often it is impossible to tell what the original rock was.
The most obvious structural feature of gneiss is the banding of the minerals.The bands of minerals is often referred to as "MARBLING".
Each mineral has separated out into a discreet layer-foliation- and these layers have been greatly twisted and contorted by the pressures that formed the rock.
Sometimes a layer of mineral will have been pulled out into a series of lenses.
Part of the rock may have melted into granite, and the molten material may have been squeezed into cracks throughout the outcrop. This would give veins of quartz and/or a complex mess of metamorphic and igneous rock-migmatite (mixed rock).
A quartz vein so formed is very sinuous, like an aerial photograph of a meandering river.
The photo below illustrates the Popple Hill roadcut showing the granitic veining.
To log a find to this earthcache you will have a few questions to submit to me via email
Firstly: What colour is Popple Hill gneiss?
Secondly: Which general direction does the marbling(mixture of rock and colour) occur and is this consistent with the cleavage? Note:Cleavage, in structural geology describes the tendency of a rock to break along preferred planes of weakness.
Some amateur geologists refer to cleavage as foliation. In gneiss the foliation is more typically represented by the banding due to segregation of mineral phases.In this rock cut the banding is visually observed in colour and line directionality.
Thirdly:Go to N44.17.382 W075 23.956. You will see drill marks. What difference is noted regarding this specific drill mark to the ones along the opposite side of the road and WHY?. Explain your answer as it relates to the rock geology.
Lastly...to receive a smiley, you are expected to take a photo of your favourite rock feature of this rock cut and upload to the earthcache gallery. Include your GPS in the photo.
While there may be ample parking along the side of the road of Route 58( there is a wide paved pullover section for the entire earthcache) and while the location by GPS coordinates may suggest to stop here, the Popple Hill road is highly suggested for parking because it has much less traffic and offers more security for your car stop. As with any geocaching/earthcaching pullovers along a busy roadway, safety is a priority and common sense awareness of traffic prevails for the visit.
Thank you to the saged "info" from the CCC- some revisons have been made to the earthcache requirements. Please feel free to submit any photos you would enjoy sharing with others- particularly interesting photos of the marbling or the veins in the gneiss that you believe conjure imaginative "perceptual" shapes that might be enjoyed by viewers. Thank you.