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26 March 2012

Monday Geology Picture: Serpentinized Harzburgite in Thin Section

For this week’s Monday Geology Picture, I thought I would share a picture of peridotite in thin section viewed under a microscope. This particular  peridotite originates from the Samail Ophiolite, Sultanate of Oman, and is a weakly-deformed harzburgite that is ~40% serpentinized. You can see the fine network of serpentine veins throughout the sample. The brightly-colored patches are olivine and pyroxene minerals. I really enjoy looking at rocks in thin …


12 March 2012

Monday Geology Picture: Listwanite Hills in the Sultanate of Oman

Today I am going to share some pictures of listwanite (also sometimes spelled listvenite, listvanite, or listwaenite), an unusual  rock type that I bet even some of the well-educated geologists who read this blog have never seen or even read about. I don’t even think there’s a wikipedia entry about listwanite. Perhaps I’ll write one after my thesis defense next month. Listwanite forms when ultramafic rocks (most commonly mantle peridotites) …


18 January 2012

Mantle Peridotite in the Samail Ophiolite, Oman

Over the past couple of weeks, I posted pictures of pillow basalts and sheeted dikes in the Samail Ophiolite, Oman. To round out the crustal ophiolite sequence, I thought I would post a couple of pictures of mantle peridotite in the Samail Ophiolite. As you can see in the below pictures, mantle peridotite in the Samail Ophiolite is generally highly-weathered and a dullish brown color. Harzburgite tends to be a …


9 March 2011

Geology Word of the Week: S is for Speleothem

Posing with a pseudostalagmite, Oman, January 2009. def. Speleothem: An encompassing term used to describe all types of chemical precipitates that form in caves. If you’ve ever been in a cave, you’ve probably seen speleothems. Speleothems generally precipitate from groundwater which has percolated through the bedrock surrounding the cave and leached various elements and compounds. When the enriched water reaches the cave, changing conditions (a large open space has very …


17 February 2011

Geology Word of the Week: P is for Peridot

Peridot gemstone. Image taken from here. def. Peridot: Peridot is a gem-quality olivine [(Mg,Fe)2SiO4], a beautiful green mineral found in mafic to ultramafic rocks. My engagement stone is a peridot– my fiance was pleasantly surprised that my favorite gemstone is among the cheaper gemstones. Though far less durable than diamond, peridot has a beautiful green color which I love. Most gemstones have alter ego mineral names. Below are some examples: …