Water-hogging settlers and very purple rocks

Fluorite at an abandoned mine near Jamestown, Colorado

Back in the 1880s, George W. Coffin lived along St. Vrain creek, which flows in a mountainside ponderosa pine forest northeast of Boulder, Colorado. He made good use of the water, for irrigation. So did the Left-Hand Ditch Company, even though they lived a ways south of it — closer, actually, to another drainage called Left Hand Creek. Left Hand Creek ran smaller than the St. Vrain, with not enough water to supply the company’s business. So the company dug ditches to divert water from the St. Vrain into James Creek, and from there into Left Hand Creek, and then through still more ditches so they could sell it to irrigators. One year, there was a bit of a drought. Ol’ Mr. Coffin tore out part of the Left Hand Ditch Company’s dam, effectively restoring the natural flow of St. Vrain Creek — toward his own property where by rights, he thought, it ought to go.

The Colorado Supreme Court decided otherwise, thereby laying down (in 1882) one of the still-standing cornerstones of Western water law: first come, first serve, even though the Left Hand Ditch Company diverted the St. Vrain into an entirely different drainage to the exclusion of people living on its banks. They’d gotten to it first, and Coffin was out of luck.

This week, more than 100 years later, we studied the case for Charles Wilkinson’s environmental law class at CU Boulder. And today, in a happy convergence, I got to see Left Hand Creek for myself.

The occasion was a field trip for mineralogy class to an abandoned fluorite mine near Jamestown, presumably named for the once controversial James Creek. I’m learning through my law classes and mineralogy that this whole area was a hotbed of discovery. For example, the nearby resort town of Telluride, Colorado is named for tellurium, the only element with which gold will partner to make an ore (otherwise, gold occurs by itself).  We saw several historic mine shafts along the road to Jamestown, which in places parallels Left Hand Creek.

And at the fluorite mine, I learned one amazing way the Earth spewed forth the minerals that so richly rewarded the first white Westerners.

TA Dave Brown performs a secret handshake with a streak of granite (unrelated to the fluorite mine)

Dave Brown, the lab teaching assistant and a master’s student in the CU Boulder geology department, explained it like this:

Much earlier in Earth’s history — many millions or even several billion years ago — a blob of magma was cooling just beneath the Earth’s crust at what would become Jamestown. Trapped inside of it was water.

As the magma cooled (which took hundreds of millions of years), more and more water was concentrated in that wet little prison until the pressure became so extraordinary and the heat so intense that the water flashed to steam and escaped, up into fissures near Earth’s surface. It carried with it all the minerals that hadn’t crystallized in the magma — including some, like fluorite, that are valuable to people.

Fluorite so purple, it rivals a student's notebook. Notebook courtesy of Rae Ann Orkild-Norton.

Fluorite is used in processes to manufacture steel, aluminum, glass and enamels. In some cases it’s used to make telescope lenses (aha! a connection with my astronomy interest!).

I continue to be fairly shocked that I like mineralogy so much. Somehow it didn’t hit me nearly two decades ago — when I was a distracted undergrad — how cool it could be to take a walk outside and notice all around you the story of Earth in its rocks.

We saw several other mineral environments on this field trip — sedimentary, igneous and metamorphic. I won’t go into more detail here, but if you’re interested for any reason, feel free to check out this Picasa photo album (my study guide) showing some examples.