Rhodochrosite - MnCO3 The Alma King, largest known rhodochrosite crystal; state mineral of Colorado. Specimen from Denver Museum of Nature and Science; photo by author
What are these things? — Stylolites
See these thin little squiggly gray lines in the rock in the photo above? These are what you call stylolites. Stylolites are caused by pressure dissolution, meaning that a large amount of stress was applied to the rock in a direction perpendicular to which to stylolites are formed. Because of this pressure applied, there’s a dissolving… Continue reading What are these things? — Stylolites
Words to know: Palimpsest
On my very first ever day of geology class, my geology professor introduced me to the word palimpsest, which is a text written over other texts. Normally the word is used to describe parchments in which the original writing has been removed and written over by new writing, However, the Earth itself truly is the ultimate… Continue reading Words to know: Palimpsest
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
Oolitic limestone
Limestone with ooids and shells, viewed through a hand lens
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
Some perspective on (geologic) time [w/ the Acasta gneiss!]
Due in large part to the lasting legacy of Christopher Columbus’s expeditions, North and South America will forever bear the mark of the “New World.” Whereas Europe has cathedrals centuries older than the United States itself, North America appears to not be able to offer much in terms of relics of antiquity. The earliest humans… Continue reading Some perspective on (geologic) time [w/ the Acasta gneiss!]
Denver Museum of Nature and Science, Prehistoric Journey
Field Museum of Natural History, Evolving Planet
A message from a geologist to people who believe in “overlapping magisteria”
In the ever persistent spirits of Clarence Darrow and William Jennings Bryan, Bill Nye the “Science Guy,” and Ken Ham, president of the Creation Museum, had a good old-fashioned evolution vs. creationism debate earlier last month. However, this “debate” that Nye and Ham have once again re-ignited is futile, seeing as there can never actually… Continue reading A message from a geologist to people who believe in “overlapping magisteria”
Emily Zawacki, Ph.D. 