Mineralogy

Photo of the Week

Matt Herod February 15, 2017

Keepin’ then comin’! This weeks photo is brought to you by Immageo as per usual. It can be found: here

The image was taken by Dmitry Tonkacheev, IGEM RAS, Moscow, Russian Federation.

Dmitry writes, “This is Co-bearing sphalerite, synthesised using gas transport method at 850C looks like the Christmas Tree. Although presented intergrowth of crystals was made in the laboratory, there are some natural samples, that comes from Africa. Green sphalerite from Congo can be used as jewellery.”

I have to chip in that incorporating Co into minerals can often lead to some very unsusual colours. For example, cobaltoan calcite is brilliant, neon pink.

Quartz over Malachite on Cobaltian Calcite

Cobaltoan Calcite from Katanga, Congo. (Source)

Photo of the Week (Approximately)

Matt Herod November 7, 2016

The truly insane photo above shows “Different generations of calcite cements in Late Miocene seep carbonates (Piedmont, Italy; cathodoluminescence microphotograph)”. It was taken by Marcello Natalicchio, University of Hamburg, Hamburg, Germania – Source.

This photo was taken using a cathodoluminescence microscope which is both a standalone tool or can be an adaptation to a scanning electron microscope. In cathodoluminescence microscopy an electron beam is fired at the sample which causes it to emit light (luminesce). The chemistry of the material being imaged determines the wavelength of the light emitted. Cathodoluminescence microscopy is a very useful tool for visualizing interior features such as fabrics, growth periods or other changes in the crystal interior that are not visible using traditional visible or polarized light microscopy. In the picture above the cathodoluminescence is being used to show the different stages of formation of a calcite cement.

In the geosciences cathodoluminescence microscopy is most frequently used to investigate the growth and deformation history of sedimentary carbonates, the interior structure of fossils, diagenetic processes, growth and dissolution of igneous and metamorphic minerals, and the growth of hydrothermal veins. The reason cathodoluminescence microscopy is so useful is that it allows the interior chemical variability of the sample to be imaged at the microscale without destroying the relationships that exist between the different stages of crystal growth.

I’m not counting Photo of the Week posts any more. The photo updates to the blog will now come whenever I feel like it. To be honest, I’m not sure how often I’ll feel like it. Although, now that daylight savings time has ended that may be more often since getting outside now involves enveloping myself in several layers of fabric. Also, daylight savings time is stupid, and I hate it.

Cheers

Cruisin’ for Deep Sea Vents

Matt Herod April 11, 2016

My friend John Jamieson, who is now a prof in the geology department at Memorial University in Newfoundland and Canada Research Chair in marine geology and is also a former GeoSphere guest poster is currently on a research cruise near Fiji. John researches deep sea vents, aka. black smokers/seafloor massive sulphide deposits that are exhaling super heated water at tectonic plate boundaries around the world. These vents are modern analogues of the conditions in which volcanogenic massive sulphide deposits form, which are major sources of iron, copper, lead and zinc around the world.

Watch the really cool video below to learn all about the cruise and why we care about black smokers and mapping the ocean floor.

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While you’re at it, check out some of the other awesome videos from the Schmidt Institute for Ocean Science!

Photo of the Week #51

Matt Herod March 7, 2016

I’m getting back in the bog saddle. After a brief hiatus as I was adjusting to the life of a real, productive member of the PGS (post grad school) world I am good to go for blogging again. Enjoy the photo of the week!

Sphalerite’s “Transformer” by Dmitry Tonkacheev, IGEM RAS, Moscow, Russian Federation

The text that follows is a technical description of the photo by the photographer, Dmitry Tonkacheev.

Presented intergrowths of the infinite number of dark-brown sphalerite’s and arborescent crystals of gold were synthesized using gas transport method at 850 centigrade degree during 20 days by Dmitry Chareev from the Institute of Experimental Mineralogy RAS in Chernogolovka city, Moscow Region while we were working on the project of Russian Scientific Fund in the Institute of Ore Geology, Petrology Mineralogy and Geochemistry RAS.
The main aim of this project was the determination of the maximum possible concentration and chemical state of some trace elements in the most abundant sulfides, synthesized using different techniques, including in ZnS. We obtained crystals of Fe-bearing sphalerite with simultaneous incorporation of Cd, Mn, In, Se and Au. The concentration of gold reaches 3,000 ppm (0.3 wt.%). This is amazing for natural sphalerite. The next goal was in-depth-study of the influence of the presence of Se, In, Fe, Mn on Au concentration and also lattice parameter in ZnS. In this connection in the furnace-charge of Fe-bearing sphalerite, different admixtures were added in different combinations or severally.

According to LA-ICP-MS data Fe did not encourage Au annexation (73±1 ppm). The bulk of Au wire “boards” on the dark-brown phase surface in the form of fascination crystals (usually arborescent). Some of them looks like a weapon from the “Transformers” arsenal or parts of his armor. Also bright diamond luster of this creature makes our “Knight” even more ultra-modern.

Militiamen’s profile was confirmed by twisted skeletal crystal on the transformer’s head. It looks like ostrich plumage or horn, which were the main attribute in the plate armor of ancient warriors and indicated about their noble birth. Truly, it is a king of all sulfides. The good news for us is the fact, that the coarsening of this bellicose subject is approximately 1-2 mm.