Specimen of the Month
Current Specimens
November's Specimen of the Month
Platanus sp.
Sycamore leaf – BCGM 80
Ludlow Member, Fort Union Formation, Paleocene Epoch (63 million years old)
Fallon County, Montana
Donated by Bob & Betsy Campbell
As I shuffle through piles of crunchy leaves after watching them change color and drift to the ground, I’m reminded of an interesting fossil plant in the Geology Museum’s collection. This fossil leaf is from an ancient species of sycamore tree and is an excellent example of carbonization. The leaf was encased in mud which, over millions of years, became a fine-grained sedimentary rock called mudstone. After the leaf decayed, the thick veins of the leaf left behind impressions, and only a thin carbon film remains showing its original outline. Sixty-three million years ago, the sycamore trees lived along rivers and streams that were flowing toward the northeast from the newly forming Bighorn Mountains in Wyoming. The Ludlow Member contains the record of rocks and fossils from the lower part of the Paleocene Epoch - a period of time shortly following the extinction of dinosaurs 65 million years ago.
Past Specimens
October's Specimen of the Month
Hemimorphite
Zn4(Si2O7)(OH2)•H2O
Durango, Mexico
Donated by Bob & Betsy Campbell
This beautiful mineral is a member of the sorosilicate mineral class, which refers to its chemical structure having two silicate molecules sharing one oxygen. The crystals are strongly piezoelectric and will generate electricity when significant pressure is applied. Quartz is another example of a piezoelectric mineral, and is used to keep accurate time in watches and clocks. Hemimorphite has a hardness of 41/2-5 on the Moh's Hardness scale (1 is very soft, 10 is very hard). This mineral is used as an ore of zinc, while other zinc silicates are used as food additives, and in the manufacture of plasma displays and fluorescent lamps. The name hemimorphite derives from the semi-spherical crystal growth habit, similar to a pompom.
This specimen was chosen as this month's feature because it is our museum manager's favorite. Send us the name of your favorite rock, mineral, gemstone or fossil and look for it in an upcoming feature!
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