Arizona Mining Review: Touring Florence Copper In-Situ Recovery Project
“We are probably the most regulated mine in the state of Arizona”
Dan Johnson, VP & General Manager of Florence Copper, Inc.
For over fifty years, the Poston Butte porphyry copper deposit near Florence, Arizona, has been on the radar screen of Arizona’s mining industry. An estimated 2.4 billion pounds of copper, hosted in Proterozoic quartz monzonite, lies buried beneath 400 feet of overburden. In the 1960s, plans were afoot to extract the copper using open pit technology. But the copper-rich oxidized zone, which extends from a depth of 500 feet to about 1,200 feet, resides in the water saturated zone and is more well-suited to in-situ recovery.
On 24 July 2018, Dan Johnson, Vice President & General Manager of Florence Copper, and Stacy Gramazio, Manager of Communications & Public Affairs, gave the Arizona Mining Review team an early morning tour of the facility. You can view this 15-minute video at https://tinyurl.com/AMR-FlorenceCopperTour .
Florence Copper is in the final stage of building a $25 million production test facility, designed to harvest 1.5 million pounds of copper annually for several years. Following successful proof of concept, Florence Copper has plans for a larger plant to recover 55 million pounds of copper annually for the first 6 years, and 85 million pounds annually for another 14 years. Over a 20-year lifespan, Florence Copper estimates the recovery project will yield ~$3.4 billion dollars in revenue.
In-situ copper recovery is a 3-phase process: Phase 1 - injection of the active fluid (99.5% water with 0.5% sulfuric acid) with a pH similar to household vinegar; Phase 2 - extraction of the pregnant, copper-rich solution; and, Phase 3 – using electrowinning, a process first pioneered in the Globe-Miami area in the late 1960s, to produce ~ 100-pound copper cathodes that are 99.999% copper.
According to Dan Johnson, this vertically integrated in-situ production approach places Florence Copper’s in the top 5% in terms of efficacy of copper mines in the world.
Full commercial production is scheduled to begin in two- to three-years. The plant will require about 170 full-time employees. In addition, they will employ ~ 75 full-time contract drillers, and several hundred workers in support service roles - as suppliers and consultants - bringing total employment to about 500 people.
Other Online Resources:
- Florence Copper, Inc https://www.florencecopper.com/
- Recovery of Copper by Solution Mining Techniques by David Briggs (2015) http://repository.azgs.az.gov/uri_gin/azgs/dlio/1641