War Memorial #848 ~ Newtonmore EarthCache

This EarthCache takes you to the war memorial in NewtonMore. Take your time to stand and remember the war dead here and pay your respects. This is a two part EarthCache, that starts where the path from the road leads up the memorial. 

First we are looking for a geological feature known as a calthemite. If you look at the blocks of stone that border the pathway, they are joined together by mortar . Mortar is traditionally a mix of lime and sand. Lime consists of  calcium oxide, gained from heating limestone. At first there would have been neat lines of mortar between the sandstone blocks, but has time has gone on, and the structure has been exposed to water, the calcium oxide reacts with water to form calcium hydroxide. Over time, rainwater carries calcium hydroxide in a solution, which when it comes into contact with air, it reacts with carbon dioxide and calcium carbonate is preciptated.

In a cave the precipitation of calcium carbonate forms both staligtites and staligmites. Though in a location outwith of a cave, these deposits are known as calthemites.  A calthemite is a deposit derived from concrete, lime or mortar, and they grow under man made structures, and look like cave structures.

Calthemites can appear in many forms, which are :

Flowstones, which looks like a flowing river off calcium carbonate, this tends to be rippled.

Straw Stalagtites, which are long thin straw like structures.

Calthemite stalagmites, which are a build up of calcium carbonate on the floor, which gradually gain height.

Calthemite rimstones, these form on the  floor as a gradually sloping structure.

When a stalagtite and stalagmite join, it is known as a column.

This being an earthcache, in order to log it, I ask that you answer some questions. Please send them to me, and do not include them in your log.

​1. If you look at the wall you can see an example of a calthemite, this is flowstone. 

​2. What colour is the calthemites, why is this?

​3. How long is the flowstone, and how far out of the wall does it protrude, please describe it. 

Now it is time to walk up to the war memorial itself. The memorial is made out of granite. 

Granite is a common type of igneous rock. Igneous rock  is one of the three main rock types , the others being sedimentary   and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallisation either below the surface as intrusive (plutonic) rocks or on the surface as  extrusive (volcanic)  rocks. Granite can be white, pink, or gray in colour, depending on their mineralogy.  Granitic  rocks mainly consist of feldspar, quartz, mica and amphibole minerals,  which form an interlocking matrix of crystals.

Though we are not here to look at the granite in general , we are here to look at one aspect of it, an item called a Xenolith. So what is a Xenolith? If you look at the war memorial, you will notice some large marks, which stand out from the rest of the granite. These  are xenoliths.  Xenolith is greek for a foreign rock.  A xenolith is a rock embedded in magma while the magma was cooling.  As the molten material rises, it tears off bits and pieces of the magma pipe, or roof / wall of a pluton in which it was travelling in which it is traveling. These bits and pieces, trapped in the magma but not melting into it, become xenoliths. Crystals that are torn from the sides of magma pipes are called xenocrysts. As the magma flows out on to the surface of the Earth, or remains as a body within the crust, it is cooled, and various types of igneous rocks could be formed. Xenoliths usually have a different colour and density when compared to the surrounding rock, they can be small or large. Their shape can tell us something as well, 'fresh' xenoliths, ie frozen quite soon (in geological terms) as they were ripped from the parents rock could have sharper edges. Older ones would be more rounded  as more 'attacked' and destroyed by the magama. 

Basically a xenolith is a piece of rock that has fallen off into the magma.

Now there are EarthCaches which look at xenoliths, but we are here to look in a bit closer detail.

Xenoliths can be of many types of rock,  and can be defined as a xenolith of a type of rock, so if for example we were talking about peridotite would be a xenolith of peridotite. 

Below are a few examples of xenoliths of rocks.

Xenoliths of Peridotite . Periodotite is a coarse grained igneous rock, which consists mainly of the olivine and pyroxene, which are minerals. It is a dominant rock in the upper part of the mantle of the Earth. It can be bright to dark green with some specks of black, though some peridotitic rocks may be  blue, brown, and red.

Xenoliths of Gabbro.Gabbro is generally coarse grained, with crystals in the size range of 1 mm or greater. It is formed from magnesium and iron rich magma, deep beneath the crust of the earth. It can be a dark grey coloured rock.

Xenolliths of Pyoxenite. These are often coarse grained, with individual crystals , which can be up to 17cm in length. Pyoxenite is formed as an accumulation of crystals at the base of the magma. Pyroxenites can be found as layers in peridotite masses. Pyroxenite is uncommon at the surface because it occurs predominantly deep in the crust or in the mantle. It can be black . dull coloured, but may also contain green or red crystals.

Xenolths of Slate. Slate is what is known as a metamorphic rock, this means it has been changed from its original form by pressure and  / or heat. It is finely grained, and has planes, which are like fine lines. It can be green, grey, or black in colour. 

This being an earthcache, in order to log it, I ask that you answer some questions. Please send them to me, and do not include them in your log.

(a) Please find and measure the largest xenolith, how wide and long is it?

(b) Please describe the xenoliths you can find on the memorial, in terms of colour, shape, feel and what they look like.

(c) Using the above information, what type of xenolith can you find here? 

This being an EarthCache, in order to log it, I ask that you answer  the above questions. Please send them to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile.