The coordinates here take you to a plaque dedicated to John Edward Marr who was born here.
The plaque is made from slate and this plaque gives clues that this piece of slate started life as a sedimentary rock before being transformed into slate.
1) Describe the slate - mention the colours and any distinctive features
2) What mineral may be present in the slate to give it it's colour?
3) How many bands can you see on the slate?
4) Explain why these bands show that slate is sedimentary in origin.
5) Please add a photograph or identifying item such as your GPS, please don't include the plaque in the photo so as not to reveal the answers.
Please use the messaging facility to send your answers to me. Once you have sent your answers, you don't need to wait for a response before logging the cache.
This slate is likely to be from the Borrowdale Volcanic Group. This is created as layers of volcanic ash accumulate over time, forming a sedimentary rock. As these are laid down in layers, when a new material falls on top of the old material, this will cause a difference in colour, You can see this in the presence of bands in the rock. The volcanic ash deposits undergo compaction and cementation, transforming into a solid rock structure. Through the geological process of metamorphism, which involves heat and pressure, the sedimentary rock evolves into the distinctive green skate.
Slates can be various colours. The colour of slate is determined by the minerals it contains.
For example, if slate looks green, it's because of chlorite, a type of common mineral that forms during the initial phases of metamorphism when rocks are changed by heat, pressure, and chemicals. When there's a lot of chlorite in slate, it makes the slate appear green.
Blue slate forms when clay minerals, like illite, undergo metamorphism under high heat and pressure. The inclusion of finely divided pyrite contributes to the distinctive blue colours in the slate.
Purple slate comes from haematite, an iron oxide. Haematite is present in slates formed under oxidizing conditions from iron deposits, making it the most enduring form of iron that remains unaffected by exposure. While not visible to the naked eye, haematite can be identified by its distinctive purple color.