This Unique Millennia Rock is situated in Chislehurst, Bromley Borough, Kent and was a gift in 2000 from
The Highland Council of Scotland. 20 tonnes was shipped from Scotland in the form of large nuggets.
To claim this EarthCache and log as found on the Geocaching.com website you must visit the Millennia Rock and answer the following questions replying to me through my profile. It may also be necessary for you to research online for minerals found in the stone.
This Stone is totally unique compared to others found close by in so much as it has the Mineral Quartz beautifully visible on the one side.
The Lewisian gneisses The oldest rocks in the British Isles are the Lewisian gneisses. These ancient rocks show evidence for a long history of shearing and recrystallisation punctuated by periods of igneous activity. Lewisian rocks can be found in the Outer Hebrides and along parts of the NW Scottish mainland, the rocks are named after the island of Lewis. The oldest Material is termed “Scourian” – named after the village of Scourie in Sutherland.
Most of this material probably started "life" as various types of igneous rock - most likely the roots of old volcanoes. It is in this environment that the modern Earth's crust is largely formed. So the continental crust that forms the underpinnings of northern Scotland formed as the roots of old volcanoes.
What happened was that the old magma chambers, once solidified, have been squashed about and sheared. It’s this process that reorganizes the once igneous rock into gneiss - and in the process the old igneous minerals are recrystallised to make new "metamorphic" minerals. The bulk chemistry doesn't change but the material changes its organisation - or mineralogy. In the Lewisian the oldest crust formed about 3000 to 2700 million years ago. It sounds a long time ago, but the world’s oldest surviving continental crust is about 4000 million years old! The shearing that reshaped the crust happened about 2450 million years ago, in an event called the “Badcallian”.
These ancient rocks have counterparts in Canada and Greenland showing that Scotland once belonged to the same land mass, known as Laurentia. England and Wales belonged to a different land mass, Avalonia, which collided with Scotland approximately 430 million years ago when the Iapetus Ocean closed. The opening of the Atlantic Ocean (approximately 60 million years ago) and then the loss of the land bridge between England and France, at the end of the last ice age, finally created the British Isles as they are today, with Scotland well and truly stuck to England's "north coast!
For hundreds of millions of years, these rocks were buried beneath the surface which meant that the intense heat and pressures helped to form the growth of the new minerals in them, It is thought that the original rock was probably sandstones and limestone or igneous rocks like basalt and granite About two million years ago the ice age came to Lewis. Glaciers engulfed the land and the sea forming the smooth rocky landscape you can see today. When the ice melted twelve thousand years ago, the sea level rose - flooding river valleys and lower ground and creating the lochs and drowned valleys of the isles. As the climate improved the land became alive, soil formed and plants and woodland returned. Peat developed on the poorly drained ground and extended upwards and outwards to cover large tracts of land. It buried the natural rocks and the stone monuments that had been erected by early settlers. Later peat became the chief source of fuel for the islands.
Quartz is one of the most well-known minerals on earth. It occurs in basically all mineral environments, and is the important constituent of many rocks. Quartz is also the most varied of all minerals, occurring in all different forms, habits, and colors. There are more variety names given to Quartz than any other mineral. Although the Feldspars as a group are more prevalent than Quartz, as an individual mineral Quartz is the most common mineral.
Crystals, which are hexagonal in shape, vary in shape and size. Quartz crystals are unique and very identifiable with their pointed and often uneven terminations. Crystals can be in enormous prismatic and stubby crystals, or in pointed aggregates of such crystals. Crystals are usually striated horizontally, and are sometimes doubly terminated. Quartz crystal habits include drusy, grainy, bladed, as linings of geodes, as rounded waterworn pebbles, radiating, as pointy pyramids on a matrix, as dense agglomerations of small crystals, massive, globular, stalactitic, crusty, in nodules, and in amygdules.
Questions to qualify for a find.
Please e-mail all answers (they will be checked) to me via my profile; all logs not supported by an email WILL be deleted.
1, What is the name of the largest island in the Outer Hebrides from where the rocks take their name from?
2, What helped form the growth of minerals in the rock?
3, On the road side (west) of the rock in the top right corner this is slanted, please describe what characteristic effect the Quartz minerals in the rock have? you will have to visit the rock to ascertain this.
4. It is no longer a requirement to post a photo of yourself at GZ but a cheesy Selfie of you will make us laugh. Other than that one of your GPS at the GZ would be boring but show your not an armchair Cacher. Many thanks for taking part in this EarthCache.
If you’ve enjoyed this then go find the different Bromley Borough Millennium Rock @ Millennium Stone - A Gift from the Highlands GC3WJNR by The Creepy Crawlies. This Stone is totally different from the Chislehurst one as there is no quartz present in this example, go find it and experience the difference in the 2 rocks.