Larvikite
Larvikite is a coarse-grained igneous rock (a type of monzonite) from Norway, prized for its iridescent blue or silver sheen caused by feldspar crystals. It is formed from the slow cooling of magma deep beneath the Earth's crust, approximately 298 million years ago.
Light and dark larvikite are two variations distinguished by their base color and the intensity of their shimmering blue or silver flashes.
Light larvikite - lighter bluish-gray with subtle flashes of silver or blue.
Dark larvikite - Dark bluish-gray, sometimes with golden-brown overtones, it has a more intense, dramatic flashes of blue or silver.
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-gray hue. Quartz, often in the form of small grains or veins, adds depth and luster to the rock's surface.
In order to log a find against this EarthCache, you will need to visit GZ and answer the questions, you can send your answers to me via the Geocaching messenger facility or email
Questions
- Is this dark or light Larvikite?
- What size are the crystals you can see?
- Describe the colours in the cladding?
- Did this rock cool slowly or quickly? Why do you think this?
- Take a photo of yourself (you don’t need to show your face) at GZ, or an identifying item, being careful not to reveal any of the answers to the questions.