July 1, 2012
A gathering of geologists, planners, aggregate operators, and others sparks interesting dialogue on geology and mining.
I recently attended the 48th Forum on the Geology of Industrial Minerals, hosted by the Arizona Geological Survey. This has always been one of my favorite gatherings, and this year was no exception. The event offered three field trips to industrial mineral operations, two and a half days of technical presentations, guest trips, an outstanding banquet, and unlimited time to renew old friendships and make new acquaintances. The meeting is attended by geologists, planners, aggregate operators, drillers, teachers — practically anyone with an interest in industrial minerals. There are seasoned veterans who have attended for more than 40 years, folks who come once in a while, and newbies. Many folks bring along guests and make a vacation of it. All are welcome and treated like family.
The very first paper caught my interest. The speaker described a quarry providing limestone for a cement plant in Maryland. The quarry contained limestone, dolomite, basaltic rocks, ash flow, sandstones, and a slew of metamorphic rocks. The whole pile of rocks has been twisted and tilted together, which greatly complicated the correlation of exploration core logs. Geologic maps, geochemistry, petrography, and radiometric dating of selected rocks were used to create a geologic model, resulting in more confident correlations and an overall better use of resources.
Another paper described a limestone quarry in Arizona that sold a variety of products ranging from the highest quality product, used in swimming pool plaster, to the lowest quality, used to replace some of the cement in concrete. Products were chosen based on the brightness of the rock, which can be anticipated based on geologic parameters. Consequently, the mining process utilizes geology to maximize the use of the resources.
Yet another paper described a new law in Arizona that requires counties to include the protection of aggregate resources in their plans of growth and development. That was followed by a paper that described how geology was used to characterize the quality of gravels in the Agua Fria River valley, a major source of gravel in the Phoenix area. There was considerable discussion on how to use geologic maps and data as a basis for protecting the gravel resources.
The meeting included a mid-conference field trip around the Phoenix area. To my surprise and delight, I was handed the microphone on the tour bus to describe the geologic research I had done on gravels along the Agua Fria River, particularly how operators use geology to reckon with some of the quality issues.
The field trip included a stop at a gravel pit along the Salt River. The topics of discussion ranged from operating issues, such as metal wear, to geologic issues, such as the quality variations in different gravel layers.
Imagine being in a pit with a bunch of geologists, walking around, heads facing the ground, nudging rocks with the toes of their boots. Occasionally, one will bend over, pick up a rock, and gaze into it. The rock might end up in their pocket or, more likely, be dropped back to the ground and kicked aside.
I love it!
If any of this catches your fancy, you might want to attend a future forum. They are held in the spring; usually in the United States. However, the next two will be held in Jamaica and England. I hope to…..
See you at the forum.
Bill Langer is a research geologist who spent 41 years with the U.S. Geological Survey.
He can be reached at