Mineral Collecting: Evolution of a Geologist

Asked to describe himself, Chris Carlson notes that he is a rock nerd, and a cursory glance around his lab quickly reveals his passion for geology. “I grew up in Northern Minnesota in the heart of the Mesaba Iron Range. My father was a geologist and a fellow rock nerd as well,” Chris says. “He was always taking the family on trips to areas that contained unique geological features. I never really realized this until I was out of high school, and then I began to appreciate these adventures.”

Lake Superior’s North Shore will always have a special place in Chris’s heart; the Duluth Complex/North Shore Volcanics Group contains a variety of notable features, including an abundance of iron ore (Volcanics and iron ore are both closely connected). The Mid-Continental Rift area offers both the casual visitor and the geologist alike an impressive display of natural beauty and geologic character. The area, which allowed for vast outpouring of early and late stage volcanics helped spurn Chris’s love of geology, starting him along a path of mineral/rock collecting that continues today in both his personal life and career. “My personal collection contains over 120 samples ranging from MN, CO, UT, WY, ID, and MI, all the way to Ontario, Canada focusing on minerals associated with volcanics. I am running out of display space at home (which is why my lab is littered with sample specimens).”

Along with his fascination for the geology of his home turf in Minnesota, Chris has developed a fondness and appreciation for Utah’s rich geological character.

The following excerpts from Chris’s journal touch on a select few of his samples, including descriptions of the locations from which they were acquired, starting with his home state of Minnesota and ending here in Utah.

North Shore of Lake Superior: Duluth Complex/North Shore Volcanics Group

Minnesota’s geology has Pre-Cambrian roots, comprised of some of the oldest bedrock in the United States at ~2.5 billion years (Ga). About 1.1 Ga there was a triple junction rift that allowed for massive outpouring of flood basalts and other volcanics that formed the current outline of Minnesota’s Lake Superior shoreline. A slightly younger series of intrusions added the majestic rhyolite cliffs signature to the North Shore area. Notable examples would be Palisade Head and Shovel Point. Remnants of the rift extend from Michigan’s Keweenaw Peninsula, Wisconsin’s Apostle Islands, and as far south as Oklahoma (from gravity data). The Minnesota mix of volcanics is impressive and world renown—a great place to pick up rocks! See photos and captions in the photo gallery below.

Figure 1: Map of the North Shore Volcanics Group, Duluth Complex, and Beaver Bay Complex along Minnesota’s North Shore of Lake Superior (Miller). Used with permission,

Alta Stock Contact Aureole: Little Cottonwood Canyon, Utah

As part of the Earth Materials class at the University of Utah, students had the opportunity to visit the Alta Stock Contact Aureole alongside professors to learn about the varied degrees of contact metamorphism within the area through metasomatic (high temperature fluid metamorphism) processes. The further up one is in the contact zone, the higher temperature variety of mineralization occurs and radiates outward/downward in a “cooling” progression. The upper zone in the contact gives way to a dolomitic marble with layers of ludwigite (Fe/Mg borate mineral), sphene, and epidote. A bit lower one can find a small radiating vesuvianite outcrop, as well as skarn-rock located along a fault and chalcopyrite vein. The area surrounding the fault is littered with garnet and green vesuvianite crystals with noticeably different coloration in the sequence of veins along the outcrop. Photo and captions appear in the gallery below.

Figure 2: Map of area surrounding the Alta Stock Contact Aureole. (Woodford, April 2001)

Mammoth Mine: Tintic Mining District, Utah

The historic Tintic Mining District was an integral part of Utah’s early economy. The area is littered with gold, silver, iron, and copper mines, as well as a variety of mines that extracted ash deposits and clays. The Mammoth Mine was a gold and copper mine. Though easily visible from the highway, this area is off-limits to the general public. I have been fortunate to be able to participate in some authorized digs in the tailings piles and will hopefully soon be able to access the interior of the mine). The majority of ore associated with the Mammoth Mine is copper in the form of chrysocolla/malachite/azurite with each stage containing more copper respectively. Other minerals present include: hematite (specular/botryoidal), calcite (all varieties), and zeolites, to name a few. Photos of the described samples follow in the gallery below.

Topaz Mountain: Thomas Range, Juab County, Utah

The Thomas Range is an area with some relatively rare and unique minerals. The rhyolite flows were rich in titanium and beryllium, allowing for the growth of topaz, red beryl (one of the only known locations in the world), bixbyite (another rarity), and pseudobrookite (1 of 11 known locations). There is also almandine-spessartine garnet and banded obsidian (black and mahogany varieties) among others. Photo of the described samples follow in the gallery below.

Works Cited

Miller, D. J. (n.d.). Jim Miller Homepage. Retrieved from http://www.d.umn.edu/~mille066/

Woodford, D. T. (April 2001). Boron metasomatism of the Alta Stock contact aureole, Utah; evidence from borates, mineral chemistry, and geochemistry. American Mineralogist , 513-533.