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Hugo van Schrojenstein Lantman

@hugolantman.bsky.social

Geology Postdoc at Utrecht University Mechanical behaviour of minerals using nanoindentation Fan of microstructures, petrology, metamorphism, fluids, subduction, earthquakes, stress and strain. Occasionally takes pictures of rocks.

107 Posts807 Follower480 Folgt
Justin Bank@justinbank.bsky.social · last mo.

Another very cool property that comes about from the way that crystallography controls birefringence (double refraction) is that if you cut and polish calcite on a very particular orientation, the birefringence goes away!

Hugo van Schrojenstein Lantman@hugolantman.bsky.social · last mo.

Talc is commonly found in ultrahigh-pressure metamorphic rocks, formed at depths of at least 90 km. For example, here's a big aggregate of talc still attached to a piece of kyanite eclogite, from Norway. It may be soft but it can withstand really high pressures! #MinCup26

This picture contains a rock and a scalebar with an outcrop as background. The rock consists mostly of talc, a shiny platy mineral with a light gray-greenish colour. The rock also has a small part of kyanite eclogite, a green-blue-red rock. The scalebar has black and white alternating rectangles to indicate centimeters and is 13 cm long. The outcrop in the background is weathered eclogite and is mostly dark green and dark red, and is partially covered in lichen.
Mineral Cup & Ore Cup@mineralcup.bsky.social · last mo.

#MinCup26 Round 1 Match 8: It’s a pair of soft and lovely minerals as Stichtite and Talc compete for your votes. VOTE: www.mineralcup.org/2026/vote-re... RESULTS: www.mineralcup.org/2026/vote-re...

Split photo with a rough chunk of vividly purple stichtite with occasional dark speckles and a pearly white talc with cool green undertones and a flaky surface.
Hugo van Schrojenstein Lantman@hugolantman.bsky.social · last mo.

Got to take this opportunity to show one of the coolest rocks I've ever come across: it contains both a trilobite fossil and big andalusite crystals. Monazite is also cool, though.

Mineral Cup & Ore Cup@mineralcup.bsky.social · last mo.

#MinCup26 Round 1 Match 7 It's a color-changing match of informative minerals! Time-tracker #Monazite-(Ce)'s yellow in sunlight darkens to orange in incandescent light while index mineral #Andalusite is pleochroic VOTE: www.mineralcup.org/2026/vote-re... RESULTS: www.mineralcup.org/2026/vote-re...

Split photo with yellow andalusite, backlit to show its color and its growth patterns, which have four-fold symmetry with branching dark streaks in each direction and a glassy amber-yellow crystal point in a craggy setting of smaller, lighter yellow crystals.
Hugo van Schrojenstein Lantman@hugolantman.bsky.social · last mo.

It's that time of year again, is it? Well, quartz needs your help. This absolutely incredible mineral is versatile, useful, and highly interesting, and deserves a #MinCup26 win. Attached: a quartz-rich thin section spinning in the optical microscope using cross-polarised light

Mineral Cup & Ore Cup@mineralcup.bsky.social · last mo.

#MinCup26 Round 1 Match 6 It's a classic vs a newbie as the most common named mineral in the crust #Quartz is up against an exceedingly-rare sea foam-green mineral discovered just a few years ago #Asagiite. VOTE: www.mineralcup.org/2026/vote-re... RESULTS: www.mineralcup.org/2026/vote-re...

Split photo of clear quartz points radiating from a central point, with amethyst purple at some of the tips and cool mint green asagiite in mostly log-shaped crystals, with a few blobby bits.
Hugo van Schrojenstein Lantman@hugolantman.bsky.social · 3mo ago

Inside a rock, or in outer space? This picture taken with cross-polarised light shows a garnet crystal with numerous microscopic inclusions of other minerals, which create the illusion of a starry night sky against the dark backdrop of the garnet. The width of the image is about 0.5 mm.

This is a picture taken with an optical microscope using cross-polarised light. Optically isotropic minerals are extinct (dark to black) in this light, whereas other minerals can show a range of colours from gray to basically any colour in the rainbow. The picture is mostly very dark, as it is a close-up of a garnet crystal. There are numerous tiny flecks of colour from mineral inclusions that are about a micrometer in size. Three larger bright shapes are larger clusters of mineral inclusions. The two in the middle have somewhat lobate brighter patches in the garnet itself, which is strain-induced birefringence caused by pressure preserved in the inclusions.
Hugo van Schrojenstein Lantman@hugolantman.bsky.social · last yr.

Since kyanite made it to the final of Mineral Cup, I decided to contribute. Vote kyanite! Not only is kyanite gorgeous, it's also a key metamorphic index mineral and thus one of my favourite minerals to find. Here are a few examples I've come across. See alt text for details #MinCup25 #kyanite

A single crystal of blue kyanite on a matrix of white quartz. From the Betic Cordillera, SpainA green-blue kyanite eclogite with a reddish vein of garnet, bordered by more dark blue kyanite. From Pohorje, Slovenia. 2 euro cent coin for scale.Bright blue specks of kyanite in a gray-white matrix. These rocks are originally granulite of the Baltica basement, locally transformed to eclogite. From Holsnøy, NorwayOne of the most confusing samples I have ever found, this rock consists entirely of white kyanite, muscovite and quartz - here pictured on top of a red notebook with a mechanical pencil as scale. The orange colour seems to be iron oxide from the surroundings. Before finding this, I did not know that kyanite could be white! From the Betic Cordillera, Spain.
Mineral Cup & Ore Cup@mineralcup.bsky.social · last yr.

#MinCup25 Final: After a month of learning and laughter, we’re at the final match to determine the 2025 Mineral Cup Champion! We have blue blades of #kyanite up against optical magician #tugtupite. Vote: www.mineralcup.org/2025/vote/r5... Results: www.mineralcup.org/2025/results...

Hugo van Schrojenstein Lantman@hugolantman.bsky.social · last yr.

Since kyanite made it to the final of Mineral Cup, I decided to contribute. Vote kyanite! Not only is kyanite gorgeous, it's also a key metamorphic index mineral and thus one of my favourite minerals to find. Here are a few examples I've come across. See alt text for details #MinCup25 #kyanite

A single crystal of blue kyanite on a matrix of white quartz. From the Betic Cordillera, SpainA green-blue kyanite eclogite with a reddish vein of garnet, bordered by more dark blue kyanite. From Pohorje, Slovenia. 2 euro cent coin for scale.Bright blue specks of kyanite in a gray-white matrix. These rocks are originally granulite of the Baltica basement, locally transformed to eclogite. From Holsnøy, NorwayOne of the most confusing samples I have ever found, this rock consists entirely of white kyanite, muscovite and quartz - here pictured on top of a red notebook with a mechanical pencil as scale. The orange colour seems to be iron oxide from the surroundings. Before finding this, I did not know that kyanite could be white! From the Betic Cordillera, Spain.
Mineral Cup & Ore Cup@mineralcup.bsky.social · last yr.

#MinCup25 Final: After a month of learning and laughter, we’re at the final match to determine the 2025 Mineral Cup Champion! We have blue blades of #kyanite up against optical magician #tugtupite. Vote: www.mineralcup.org/2025/vote/r5... Results: www.mineralcup.org/2025/results...

RockDefTUD@rockdeftud.bsky.social · 2y ago

Amidst all terrible news, I am sad that here it is not better. Today the VU Amsterdam announced they'll cut Earth Sciences, and fire 39 staff. 130 students are left to figure out how to finish, and an unknown number of PhDs lose their supervisors. My heart goes out to my colleagues 😳😥

Douwe van Hinsbergen@vanhinsbergen.bsky.social · 2y ago

Europa heeft geologen en milieuwetenschappers nodig, terwijl Nederland juist daarin snijdt. Op dit moment wordt 3% van de 'Critical Raw Materials' die Europa nodig heeft, hier gewonnen. De EU wil dat in de komende vijf jaar verdrievoudigen, en wel volgens Europese standaarden. Dat vergt kennis 1/n

Pete Bowden@peterlbowden1.bsky.social · 2y ago

A beautiful example of an Outer Hebrides dyke cutting the foliation in Archaean #Lewisian gneiss. Although folded by later Laxfordian deformation both the dyke and a thin apophysis exhibit near perpendicular angular discordance in the fold hinge, becoming concordant in the limbs. Isle of Harris. ⚒️🧪

A black Outer Hebrides dyke cuts across the pre-existing foliation in grey Archaean Lewisian gneiss. Thin apophysis (offshoot) and the hinge zone of the folded dyke exhibit near perpendicular angular discordance to the foliation. These rocks were folded during Laxfordian deformation and strong flattening in the limbs of the folds brought the contact of the dyke and the foliation into concordance. This outcrop is located west of the village of Rhenigidale, Isle of Harris, Outer Hebrides.