GeoPicture of the Week: Complete double rainbow encircles Australian town


For our GeoPicture of the Week, we’ve gotten used to pictures of minerals, fossils or geological phenomena – but today, I want to show you something different: a stunning, complete, double rainbow: The picture was taken from a helicopter flying over Cottesloe Beach in Western Australia. Rainbows appear because water droplets act like prisms, separating visible light into its constituent spectral…


GeoPicture of the Week: Amazing Baryte

Locality: Clara Mine, Black Forest, Baden-Württemberg, Germany*Photo : © Edgar Müller

What we’re looking at here is a picture of baryte. Baryte is a mineral consisting of barium sulfate. The mineral itself is generally colorless, and it is used industrially to extract barium. Baryte occurs in a large number of depositional environments, and is deposited through a large number of processes including biogenic, hydrothermal, and evaporation, among others. It usually occurs in lead-zinc…


GeoPicture of the Week: Amazing Rhodochrosite


  Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO3. In its (rare) pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. Rhodochrosite occurs as a hydrothermal vein mineral along with other manganese minerals in low temperature ore deposits as in the silver mines of Romania where it was…


GeoPicture of the week: The Mexican hat


When you look at these rocks – it’s quite easy to understand why they’re usually called ‘The Mexican hat': The Mexican hat is a rock formation in south-central San Juan County, Utah, United States. Interestingly, it’s the name of a mini-village (named after the formation), with 31 people inhabiting it. The formation is a 60-foot (18 m) wide by 12-foot…


GeoPicture of the Week: What Causes the Colour of Gemstones


You may have wondered exactly what is it that makes gemstones so brightly colored, and if you were curious enough to actually pursue that question, you found out that it’s all chemistry. This picture explains it: Most minerals are actually colorless in their pure form, and they are colored by impurities. The color itself is caused by the different absorption…


GeoPicture of the Week: The Lion Rock in Sri Lanka

lion rock

The Sri Lankan lion rock (Sigiriya) is an ancient palace of archaeological and geological importance. The site is dominated by a massive column of rock nearly 200 metres (660 ft) high. According to the ancient Sri Lankan chronicle the Culavangsha, this site was selected by King Kasyapa (477 – 495 CE) for his new capital. He built his palace on the top…


GeoPicture of the Week: Geologic Faults


This picture from Cornell University really encapsulates the beauty of a geologic fault – it’s like someone took it from a text book and slammed into real life. In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement along the fractures. You can see how the different layers (strata)…