petrology

Art of Geology

As a geologist, not only do you have to be good in math, chemistry, physics, history, and writing, but you also kind of need to be decent at art. These are thin sections of magmatic rocks with my accompanying petrographic sketches. For a relatively small little circle, these guys take a really long time to… Continue reading Art of Geology

petrology

Dunite

Thin section of dunite under XPL.  Dunite is a type of peridotite that contains over 90% olivine and may either be found in ophiolitic complexes or xenoliths in basalt lavas. Note the ‘bubble’ texture of the vibrant birefringent olivine grains at the top and bottom of the image, and the serpentine (gray and white) and… Continue reading Dunite

mineralogy

A tale of two CaCO3’s — Calcite and Aragonite

Aragonite (left) and calcite (right), both CaCO3; image by author Here in this photo, we clearly have two different minerals–one aragonite and the other calcite. However, they both have the same chemical formula of CaCO3. So how can it be that these two different minerals are both calcium carbonate? Aragonite and calcite are polymorphs of… Continue reading A tale of two CaCO3’s — Calcite and Aragonite

mineralogy

Barite

Barite - BaSO4 Barite, is a common hydrothermal mineral. It may also be deposited by cold groundwater solutions. The crystallization is orthorombic. Quite commonly, as in this specimen, crystals are flattened parallel to the basal pinacoid, and terminated on the edges by prism faces. Cleavages parallel both the base and the prism. Lawrence University collection, information… Continue reading Barite

mineralogy

Common minerals to know

Here are some common minerals whose names and formulas are good to know, along with some of their properties! (In rows, left to right; H=hardness, tested in lab using Mohs hardness scale) 1) Halite (NaCl) – H=3.5; it tastes salty! (yes, lick it) 2) Fluorite (CaF2) – H=4; ranges from transparent, to purple, to blue 3) Sylvite… Continue reading Common minerals to know

mineralogy

Mineral spotlight: Azurite

Azurite [Cu3(CO3)2(OH)2] To start off with a mineral is a naturally occurring crystalline solid with a well-defined composition. Minerals themselves are not rocks, but together they form the constituents of rocks.  Azurite is personally one of my favorite minerals, and is a gorgeous deep blue copper carbonate (meaning it has the carbonate ion, CO32-). In terms of volume,… Continue reading Mineral spotlight: Azurite