I have always liked slate as a stone and used it on many of occasions, whether its plating food or decorative purposes. I was quite surprised there were no earth caches on this island, so here is one to edcuate a geocacher about the marvellous rock, slate!
What is Slate?
Slate is a fine-grained, foliated metamorphic rock that is created by the alteration of shale or mudstone by low-grade regional metamorphism. It is popular for several uses, such as roofing and flooring because of its durability and rustic appearance.
The Composition of Slate
Slate is made up mainly of clay minerals or micas, depending upon the degree of metamorphism to which it has been subjected to. The original clay minerals in shale change to micas with increased levels of heat and pressure over millions of years. Slate can also have similar properties to granite, as it can contain quartz and small amounts of feldspar, calcite, pyrite, etc.
How Does Slate Form?
The tectonic environment for producing slate is usually a former sedimentary basin that becomes involved in a convergent plate boundary. Shales and mudstones in that basin are compressed by horizontal forces with minor heating. These forces and heat modify the clay minerals in the shale and mudstone. Foliation develops at right angles to the compressive forces of the convergent plate boundary to yield a vertical foliation that usually crosses the bedding planes that existed in the shale. Hence the different bands you can when you pick up a piece of slate.
To log this cache, send me the answers to the below via email or by direct message:
1. From the brief lesson on slate, do you think you could possibly be standing on a plate boundary ? If so, which one?
2. There are plenty samples lying around in the area, what colour is it? how does it feel in terms of texture and compostion?
3. What do you think created the pools of water here?
4. What is slate generally used for?
5. Log a picture with your GPS as part of the log (optional).
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