This statue was unveiled by the Queen and is one of the most popular attractions in the town. You may have to form an orderly queue to have your photo taken alongside this local legend. Perfect opportunity to look at the stars on the ground and learn a little more about granite perhaps?
At the rear of Eric, you'll notice two stars on the ground, one with the words "Galloway Granite" and one with the words "Harbour & General"
Have a look at the stars and answer these questions:
1) Have a look at the "Galloway Granite" star - describe the colours you can see and the crystal size
2) Now look at the "Harbour & General" star and describe how it looks different to the first star. Which of these stars is made from granite that cooled more slowly? Why do you say that?
3) For the star you chose as your answer for question (2), do you think the crystals are anhedral, subhedral or euhedral?
4) Take a photo of yourself at GZ, or an identifying item, being careful not to reveal any of the answers to the questions.
Please submit your answers via message though the Geocaching website or by sending me an email - there is no need to wait for a response before logging your find.
Formation of granite
Molten rock containing a high content of silica, minerals, and alkali metal oxides seeps into gaps in sedimentary rock layers before slowly cooling and solidifying underground over the course of millions of years, creating granite.
As the molten rock gradually cools over time, crystals form at different periods of time from the various minerals that are present which alters the final appearance of the granite.
Crystal Size and Cooling in Granite
In igneous rocks such as granite, the size of crystals is intricately tied to the rate at which the molten magma solidifies. Consider it akin to the process of cooling a liquid to form ice. Swift cooling leads to the development of minute crystals, resembling the rapid freezing of small water droplets in an ice tray. On the other hand, gradual cooling affords more time for crystal growth, resulting in larger, well-defined crystals akin to the formation of sizable ice crystals in a slow-freezing process.
If magma cools quickly, for example when lava erupts from a volcano, then many crystals form very quickly, and the resulting rock is fine-grained, with crystals usually less than 1mm in size.
If magma is trapped underground , it cools slowly because it is insulated by the surrounding rock. Crystals have more time to grow to larger size and crystals 2mm and larger can form.
For example, the picture below is Shap Granite, formed in the Lake District - the coin for scale here shows a slow cooling crystal as it's large in size.
Crystal Shapes
In igneous rocks, crystals can exhibit different shapes based on their growth conditions. Anhedral crystals lack well-defined faces and boundaries, forming in tight spaces or when surrounded by other minerals. Subhedral crystals have partly formed faces but are not fully developed due to limited space or competition for resources. Euhedral crystals, on the other hand, possess distinct faces and sharp edges, forming when minerals grow freely without obstruction.