Geochemistry, Mineralogy, Petrology & Volcanology

Imaggeo On Monday: Lahar in the jungle, Mexico

Velio Coviello October 5, 2020

Lahar in the jungle, Mexico. Credit: Velio Coviello (distributed via imaggeo.egu.eu)

Volcán de Colima currently is the most active volcano in Mexico where many rain-induced lahars occur every year. La Lumbre ravine is the ephemeral channel that drains the west-southwestern slopes of the volcano. In 2016, while Volcán de Colima experienced a prolonged explosive phase, several lahars were documented in this channel. One of them is shown in his picture, taken on August 13, 2016, du ...[Read More]

Imaggeo On Monday: Blue Olivine in an unusual basalt

Bernardo Cesare September 28, 2020

Blue Olivine in an unusual basalt. Credit: Bernardo Cesare (distributed via imaggeo.egu.eu)

Blue Olivine set in a matrix of pyroxene, magnetite and plagioclase in a basalt collected by the photographer, Bernardo Cesare, on the shore of the Sea of Galilee, Israel. Polarized light photomicrograph. Crossed polarizers and red tint plate. Width c. 2.7 mm. Who may have been throwing this stone a couple millennia ago? Description by Bernardo Cesare, after the description on imaggeo.egu.e ...[Read More]

Friedrich Mohs and the mineral scale of hardness

Hazel Gibson September 25, 2020

Image credit: Hazel Gibson

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

Samuele Papeschi September 21, 2020

Hedenbergite - Ilvaite skarn, Calamita, Island of Elba. Credit: Samuele Papeschi (distributed via imaggeo.egu.eu)

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]