Important: You will require a strong magnet to complete this EarthCache!!!
The listed coords will bring you to the outside of London Victoria Station at the start of a passage way leading to a well known magazine/ book seller. You will be looking for some large rock cladding that starts outside and covers the wall all the way along a passage way. You can visualise this with out actually going in the station. If you have time it is well worth studying all the cladding.
The learning element of this EarthCache is to be able to identify LARVIKITE and know a bit about this fascinating rock.
What is Larvikite?
Larvikite originates from the Larvik Fjord region in Norway. Larvikite is found only within a limited area around here of about 150 km.
Larvikite is a coarse-grained igneous rock prized for its iridescent blue or silver sheen caused by the feldspar crystals. It is formed from the slow cooling of magma deep beneath the Earth's crust, approximately 298 million years ago.
Black larvikite (above)
Blue Larvikite (above)
Green Larvikite (above)
Schiller Effect
The Schiller effect is an optical phenomenon that occurs in certain minerals under the right structural conditions. It is most commonly recognized as a shimmering, iridescent, or metallic luster that appears to move across the surface of a mineral as it is viewed from different angles or under changing light conditions.
Minerals
Larvikite comprises of a number of minerals, including feldspar, quartz, amphibole and biotite. The predominant feldspar mineral found in Larvikite is known as oligoclase, which imparts the stone's signature bluish-grey hue. Quartz, often in the form of small grains or veins, adds depth and luster to the rock's surface.
Magnetic properties?
Larvikite can be magnetic, or at least have a magnetic response, because it often contains minerals like Magnetite, though the strength of magnetism varies; some pieces might only react to a strong magnet, while others show a significant attraction, creating magnetic anomalies in geological surveys. Larvikite can be magnetic, or at least have a magnetic response, because it often contains minerals like Magnetite, though the strength of magnetism varies; some pieces might only react to a strong magnet, while others show a significant attraction, creating magnetic anomalies in geological surveys.
So to the Questions:
Please send to me the answers to the following questions either by email or the messengering system.
1. Describe the appearance of the Larvikite panels in terms of colour, crystal size and composition.
2. Would you say the Larvikite is Black, Green or blue?
3. What is the name of the larger shiny crystals and give me the dimensions please of the largest you can find. Are they silver, blue or green?
4. Run your hands over the Panels. Are they rough or smooth? Do you think the surface is natural or polished?
5. What Country is Larvikite from?
6. Run a strong magnet over the stone. Is there any attraction? Is this due to high or low levels of Magnetite?
7. Finally please take a photo of a sign at the Station with Victoria on it with either yourself or a piece of paper identifying your caching name.
References:
Geologyin.com
Hull Geology Society
Stonedatabase.com
wikipedia
geoheritage.org
geolology science.com
Norwegian Larvikite society