This earthcache will help you learn about alkali feldspar and how to identify it.
Monteith House has, at ground level, a cladding of coarse granite with large tabular (rectangular) feldspars displaying a flow texture.
Granite is an igneous rock, formed when molten rock originated from deep within the earth’s crust and cooled (either below the surface as an intrusion e.g. granite, or above the surface as an extrusion e.g. basalt lava). The resulting igneous rock is composed of interlocking crystals, the size of which depends on the time taken for the molten rock to cool. If the molten rock cooled rapidly, the crystals are small if it cooled slowly, the crystals will be large. A common building stone of the latter type is granite – due to the large crystal size in granite it is a very aesthetically pleasing rock.
How do you identify feldspar in granite?
Alkali feldspar crystals come in varying shades of pink and red, from light pink to salmon to brick red. Other types of feldspars in granite are white or clear, resulting in a wide range of granite colors. Feldspar crystals will have sharp angles and shiny crystal faces.
Look at one of the panels under the windows as indicated by the red rectangle in the photograph , then answer the following questions:
Q1. Examine the crystals in the panel and say whether this rock cooled rapidly or slowly. Give reasons for your answer.
Q2. Identify the largest crystal you can see. What colour is it? Describe its shape.
Q3. Please provide a photo of yourself or a personal item near GZ (without giving away the answers).
Answers to questions 1-2 should be sent by the message centre or email. Please DO NOT include the answers in your log.
Please send your answers BEFORE logging the cache. You do not need to wait for a reply, but if there is a problem, we will let you know.
ANY LOGS ENTERED WITHOUT ANSWERS BEING SENT WITHIN TWO WEEKS WILL BE DELETED.
