Concomitant thrusting and magmatism resulted in the development of ductile mylonites in the Calamita Schists, part of the contact aureole of the Late Miocene Porto Azzurro pluton. This mylonite is made up of stretched and recrystallized quartz layers, interlayered with thin sericite-rich levels. Sericite resulted from the crushing of contact-metamorphic minerals such as andalusite, cordierite, …[Read More]
Sometimes in order to test a theory about how processes work below the surface of the Earth, scientists need to recreate minerals found in very specific circumstances. This photograph was taken through a binocular microscope during a critical step of the creation of artificial peridotite: extraction of the artificial peridotite from its gold capsule. The …[Read More]
“Crazy Lace” is an agate collected in Mexico, which offers great opportunities for aesthetic photomicrography. Here we see the common arrangement of fibers of chalcedony (microcrystalline quartz) in parallel bands alternating with black thin layers of Fe oxides. Polarized light photomicrograph, crossed polarizers and red tint plate. width 5.4 mm. Sample kindly provided by Denise …[Read More]
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 …[Read More]
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 …[Read More]
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 …[Read More]
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 …[Read More]
Mineralogy, as a subject, often has a hard time. Despite it’s place at the core of the traditional geological sciences, and its importance in a huge variety of other subjects, mineralogy sometimes has a reputation of being complicated and inaccessible and, well, some people have even called it boring. This is also related to the …[Read More]
