GEO 192
Lamproite
Class: Rocks
Location: Mufreesboro, AR
Details: igneous
Lamproite
Class: Rocks
Location: Mufreesboro, AR
Details: igneous
It's been awhile since the last post, but here is a small but interesting new piece all the way from Arkansas - the Natural State. From the Crater of Diamonds State Park in Mufreesboro, AR this yellow-dotted rock tells the story of how the volcanic crater formed and why the park is known for all its diamonds. Those yellow/green spots are actually small pieces of the Earth's upper mantle (called macrocrysts) which are made out of olivine. Deep, deep down in the Earth's mantle (150+ km down - the crust is a max of 50km thick and the deepest humans have drilled is 12 km) diamonds are formed under the immense pressure. Lamproites like this (along with a similar mineral kimberlite) are able to transport diamond-bearing rocks to the surface - but do not contain the diamonds themselves.
Now, lamproites come in a variety of forms from the state park: magmatic lamproite - as it sounds forms from the magma under the volcano and pyroclastic lamproite - forms when magmatic lamproite volcanically explodes from the crater, are the two main types. These minerals are high in magnesium, and can also be found in a variety of different other element compositions. Now there is a lot more you can learn about lamrpoites and the geology of the Crater of Diamonds State Park in general on the link and expect more specimens from the diamond park later on from the Sholesonian.