Jersey Island Geopark II
A Geopark is about more than rocks
Jersey is a strong contender for this special designation because of our Island's exceptional geology and our important cultural heritage which forms the outstanding surroundings we enjoy every day. Whether exploring Jersey's diverse landscapes or seascapes there is lots to discover and inspire you.
Summer opening hours: March to October - 10am to 5pm
Winter opening hours: November to February - 10am to 4pm
Closed: 24, 25, 26 & 31 December and 1 January
To log this Earthcache, visit the Jersey Island Geopark and answer the following questions.
You can find 7 Jersey rocks in the Jersey Island Geopark, answer questions about 3 stones.
1: Rozel Conglomerate Formation: What is this rock also called, and how large are the inclusions?
2: Shale: How did this slate surface form? Describe the slate surface.
3: Vein of calcite: Look closely at the calcite. What is the surface structure like? Can you determine its hardness? How wide is the calcite vein?
1: Rozel Conglomerate Formation
The Rozel Conglomerate Formation is a geological deposit on the island of Jersey, Channel Islands, characterized by coarse conglomerates formed from rounded pebbles cemented together, deposited by alluvial fan processes during the Late Cambrian to Ordovician period. Located in the northeastern part of Jersey, it unconformably overlies older volcanic rocks and represents a period of mountain uplift and subsequent erosion during the Cadomian Orogeny, with sediments carried by flash floods.
2: Shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g., kaolin and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. Shale is characterized by its tendency to split into thin layers (laminae) less than one centimeter in thickness. This property is called fissility. Shale is the most common sedimentary rock. The term shale is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the narrower sense of clay-rich fissile mudrock.
3: Vein of calcite
A calcite vein is a crack or fracture surface in rocks filled with calcium carbonate (calcite) and formed by geological processes such as hydrothermal fluids or tectonic stress. These veins are important for the mechanical and physical properties of the surrounding rock because they can seal natural fractures and form an integrated solid structure. The formation of calcite veins is complex and influenced by factors such as fluid flow velocity, calcite supersaturation of the solution, and the surface texture of the cavity. Calcite has a Mohs hardness of 3 and is therefore considered a relatively soft mineral.
Picture:
from Jersey Island Geopark
Sources:
from Jersey Island Geopark
1: jerseygeologytrail.net/Rock_Types_Conglomerate.shtml
2: www.eia.gov/tools/glossary/index.php?id=shale#:~:text=Shale:%20A%20very%20fine-grained,See%20natural%20gas.
3: www.mdpi.com/2073-4441/17/10/1550#:~:text=Calcite%20veins%20are%20fractures%20or,Cai%20et%20al.