GeoLog

Geochemistry, Mineralogy, Petrology & Volcanology

Friedrich Mohs and the mineral scale of hardness

Friedrich Mohs and the mineral scale of hardness

One of the most famous identification methods in the study of mineralogy is the Mohs Scale of Hardness. A comparative scale, based on the hardness of each mineral, it is a way geoscientists can compare minerals to each other and organise them based upon an easily testable physical characteristic. Each level of hardness has a value, from 1 (the softest) to 10 (the hardest) and each number is associ ...[Read More]

Imaggeo On Monday: Hedenbergite – Ilvaite skarn, Calamita, Island of Elba

Imaggeo On Monday: Hedenbergite – Ilvaite skarn, Calamita, Island of Elba

In this photo taken on the Isle of Elba in Italy you can see several radiating crystals of greenish Hedenbergite, inter-grown with blackish coloured Ilvaite in skarn bodies. Skarn is an unique formation that formed as a result of the interaction between geothermal fluids and the host rock. In this case the geothermal fluids come from the Late Miocene Porto Azzurro monzogranite, and Mesozoic marble ...[Read More]

Colour deficient vision and the geosciences; just another way of looking at things

Colour deficient vision and the geosciences; just another way of looking at things

Like a reasonably large proportion of the population, I have colour vision deficiency (also known as colour deficient vision or colourblindness). I’m not going to get into the technical aspects of what this is like as they are covered well here and here, and you can do an Ishihara test, and other tests here, to check your own vision. The other reason I’m not going to discuss the technicalities of ...[Read More]

Imaggeo On Monday: Emoji from meteorites; impact spherule

Imaggeo On Monday: Emoji from meteorites; impact spherule

This is a crossed polarized light photomicrograph of an impact spherule; a small mineralisation made when a meteorite hits the Earth and melts the rock at the point of impact, from Barberton Greenstone Belt, in South Africa. These spherules are the only remnants of Early Earth’s meteorite impact history, from between of 3.2 and 3.5 billion years ago. In this photo you can see the K-feldspar ...[Read More]