Every Dwarf knows that there are three basic types of rock: sedimentary, metamorphic and igneous.
Sedimentary rocks are formed by dirt and silt that is deposited over time, usually as layers at the bottom of lakes and oceans. The sediment is compressed over a long period of time to become solid layers of rock.
Metamorphic rocks are existing rocks which are changed into new types by heat and pressure.
Igneous rocks are made from cooling magma. There are two types of igneous rocks: intrusive, that solidify below Earth's surface; and extrusive, that solidify on or above Earth's surface.
Dwarves also prize precious gems and crystals. Crystals can be found in any kind of stone but they all have a regular geometric shape and structure. Many crystallise from watery solutions, others from rapidly cooling lava.
Now for the practical lesson: In order to claim this earthcache you must visit the Mineral Collection at the South Australian Museum at the listed coordinates and find an example of each of the following types of rock:
Sedimentary
Metamorphic
Igneous Intrusive
Igneous Extrusive
Crystal
You will also need to note where the rock came from.
Please do not put your answers in your logs, but email them to Dwarf Owl for approval. Logs that have not been accompanied by the correct answers will be discretely queried and if necessary deleted.
Entrance to the museum is free and it is open 10am – 5pm every day except Good Friday and Christmas Day. On ANZAC Day it opens at noon. The rocks are located on the 3rd floor in the eastern wing. (There is also a rather cool meteorite collection in the same area, but this earthcache is about... well, earth!) The total collection has over 32,000 minerals, rocks, meteorites and tektites from all over the world, but only a fraction are on display. (No wonder geology is so hard for us non-Dwarves!) There are other rocks throughout the museum, including the Mawson Collection on the same floor, which you may include in your answer but you are unlikely to find all types outside of the Mineral Collection.
N.B. Do not attempt to lick the rocks – they are behind glass and the security guards will get upset.