What’s on the van? – Granite

_granite_a98-5

This week’s What’s on the van? comes from Dr Dave Waters, Curator of Mineralogical Collections and Monica Price, Head of Earth Collections.

The rock that goes home for holidays
Every year, a group of Oxford undergraduates travel to north-west Scotland to unravel the fascinating geological history of the area by studying the local rocks and how they relate to each other. They stop at various places to explore the geology, including the ‘multicoloured  rock stop’, an exposure of rocks in a road-cut north of Loch Laxford. This is where our sample of granite was collected in 1998.

It is very old, part of a suite of ancient Precambrian rocks known as the ’Lewisian complex’, named after the Hebridean island of Lewis. It formed about 1.7 billion years ago when magma – hot molten rock – was intruded into an even older metamorphic rock called a gneiss. The magma cooled down, forming crystals of different minerals: pink potassium feldspar, white sodium feldspar, transparent grey quartz, and black grains of biotite mica and magnetite.

The students learn to identify the minerals by studying thin sections of the rock, just 0.03mm thick, under a petrological microscope. This allows them to examine the distinctive optical properties of each mineral under polarised light. The Oxford Earth Sciences Image Store shows you what they can see.

Each year, this piece of granite travels ‘home ‘ with the students on their fieldtrip, and helps to teach them about the different kinds of rock they will see in the field. It is part of the large collections of rocks, fossils and minerals in the University’s Earth Sciences Department and the Museum of Natural History that are available for students to study.

What's on the van?

Advertisements
This entry was posted in What's on the van by rachelparle. Bookmark the permalink.

About rachelparle

I'm Interpretation and Education Officer at the Oxford University Museum of Natural History. I work with families, exhibitions, social media and lots of other fun projects. In my spare time I mostly like visiting other museums!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s