Basalt (igneous)

Basalt is a dark basic igneous rock, it can be an extrusive or instrusive igneous rock and forms from partial melting of the mantle (the layer underneath the crust) that is primarily made up of olivine and pyroxene. When you melt a bit of that material, then you form a magma/melt that is ‘basaltic’ in composition meaning it is basic or mafic meaning it is low in silica and rich in Mg (magnesium) and Fe (iron). Basalt is usually the terminology we give to a dark, fine grained (aphanitic) igneous rock that crystallised quite quickly giving it a that fine grained texture which basically means the crystals didn’t really have time to grow which is what happens when it comes into contact with the cold air, or erupts into the cold water. In some cases it cools that quickly forming a volcanic glass. Anyway, this lava that you have in your box is Amygdaloidal Basalt from Isle of Skye. When the lava erupts at the surface it releases the gases and volatiles it contains creating small vesicles (holes/cavities) which are then later filled with other minerals when hydrothermal fluids are running through the rock and precipitating out different minerals. So aye… your basically holding a piece of lava that erupted out of a volcano 60 odd million years ago when Scotland started drifting apart from Greenland and America and that.

Granite (igneous)

Granite is a silica rich intrusive igneous rock, manly forming plutonic rocks (magma chambers and that). Intrusive rocks form in the crust, extrusive igneous rocks form at the surface and this is when we call it lava. A granite tells you a story that it used to be a magma - because it has coarse grained crystals (>2mm) it tells you that it took a long time for that crystal to grow and form the granite. You get different types of granite but they are all usually rich in silica rich minerals such as quartz, plagioclase, K-feldspar, biotite, muscovite and amphibole. Granites can form in two main ways - when you have partial melting of the crust or by fractional crystallisation of a basic (mafic lava) or assimilation of a magma chamber where some of the outer rocks surrounding the magma chamber fall into the magma chamber and change its chemistry… this really does get complicated when you really start looking into it. The granite in your box is from the Cairngorm mountains and formed around 415 to 425 million years ago during the Caledonian orogeny - that event that I’m always going on about in my videos. depending on what you previously melted before, depends on the type of granite that forms - you can get S-type granites which form from partial melting of sedimentary/meta-sedimentary rocks, M-type granites which form from the fractional crystallisation of the mantle or I-type granites which is the partial melting of igneous rocks. There’s a lot of chemistry involved but to keep it simple - we will just stick to the basics. You get partial melting of the crust at convergent plate boundaries where two plates meet - when you have a lot of crustal thickening you usually get a lot of partial melting. When we look at a geology map of Scotland, we can actually see red blobs exposed at the surface which are the magma chambers (igneous intrusions) of ancient volcanoes that existed 420 million years ago in Scotland during the Caledonian orogeny.

Mudstone

Mudstone is a sedimentary rock that forms in deep marine environments - this can be in the ocean or in a lake where you have the suspension of fine grained sediments (<0.063mm) into a marine like environment. although sometimes we do come across other places where we can see that layers of mud have accumulated over geological time. as the sediment accumulates it usually forms thin to thick laminations of mud which compact and cement together over geological time forming a mudstone. Sometimes we can find fossils in mudstone - especially if it formed in a marine environment but in this case, the rock in your box is just mudstone. It’s from the carboniferous period (299 to 359 million years ago) of Scotland when Scotland used to be located at the equator and sometimes the sea level would rise causing mudstone to be deposited.

Red Sandstone

This sandstone is from the permian period, from the new red sandstone group of Scotland - A lot of this rock has been quarried and used in the red sandstone tennaments we see in the major cities and towns of Scotland. It formed by the accumulation of sand sized particles that were carried by the wind and deposited in desert like conditions - this is why it has a red colour because the minerals have been coated in iron oxides due to the arid enviornments. Scotland was yet again completely different during the permian period and bang on the middle of the super continent of Pangea which meant there wasn’t much water at all. We can see some large scale sand dunes in these rocks across the UK which is pretty cool and unique.

Blonde Sandstone

Gabbro

Slate

Schist

Quartzite

Marble