The Detroit City Mine- another chapter in the story of Sweet Home Rhodochrosite

        Since the difficult decision to close the Sweet Home mine was made in the fall of 2004, the demand for top-quality rhodochrosite specimens from this iconic locality has increased around the world. Rhodochrosite from the Sweet Home mine has stood the test of time as one of the most coveted and valuable collectable minerals of the past 100 years, and many newer collectors have found they are simply unable to acquire a top example since the mine’s closing. Taking into account this growing demand and the probable existence of more world-class crystal pockets along the Sweet Home vein system, Collector’s Edge Minerals Inc has begun a new  specimen mining project at the Sweet Home deposit, called the “Detroit City mine.”

Many factors played a role in the decision to mine for rhodochrosite again at the Sweet Home. After the mine’s closure in 2004, geologist Dean Misantoni continued to map the surface outcrops above the mine, comparing this to the detailed information on the underground structure, geochemistry, and mineralization of the Sweet Home deposit. This information suggested that a pocket-bearing zone might extend upwards above the old Sweet Home workings, but how far? A careful study was undertaken, and the results strongly suggested that the intersection of multiple faults created a zone which was highly likely to contain pockets directly above and behind the old Sweet Home mine ‘main raise’ workings. Detailed geochemical and fluid inclusion data further suggested that conditions in this potential pocket zone were probably right for the formation of high-quality, gemmy, “cherry red” rhodochrosite. However, as with any mineral exploration project, an indication of a productive orebody is only the beginning of a long process of evaluation, exploration, and then development. Given the significant cost of undertaking a new project like this and the risks involved, a careful, multi-year feasibility study was undertaken, utilizing all resources and information at hand. The results of this study suggested that it would be more feasible to create a new horizontal tunnel high above the old Sweet Home mine portal to intersect mineralized structures which might contain high-quality rhodochrosite crystal pockets. This new mine is called the “Detroit City Mine”, the original name of the block of claims containing the Sweet Home mine, and also a homage to Collector’s Edge Minerals founder and President Bryan Lees’ roots in the ‘Motor City.’

Sweet Home Mine area during operation.

Sweet Home Mine portal in 1993.

        Work on the Detroit City mine began in the spring of 2016, when an access road to the site of the new adit, or mine entrance (~200 vertical feet above the now-sealed Sweet Home mine adit) was upgraded, and work trailers and heavy equipment were brought on site to begin the long process of excavating a new tunnel into the side of Mount Bross. As the Sweet Home deposit is located at ~11,300 feet above sea level in Colorado’s central Rocky Mountains, the weather and working conditions can be challenging to say the least.  However, 15 years of operating the Sweet Home mine prepared the mining crew well for this new project, and veteran Sweet Home mine superintendent and all around “fixer” Graham Sutton was the perfect person to head up the new Detroit City project. Graham is assisted by a crew of 3-5 miners and numerous other contractors.

Location of the new Detroit City Mine compared to the Sweet Home mine. Summit of Mount Bross (A Colorado “fourteener”) is shown as well. Tom Praszkier graphic.

        While the project is advancing as planned, there is still a lot of work to be done to reach the first potential pocket-bearing zones. If all goes as planned, specimens could be discovered as early as mid-2018. But, as with any mining project, there are uncertainties which cannot be predicted. It is likely, however, that high-quality rhodochrosite will be found once again, perhaps even rivaling the famous pockets of the Sweet Home mine, so stay tuned!

Photos of 2016/2017 progress at the Detroit City mine (all images © CEMI)

Initial Excavation of Portal Site.

Setting concrete pad: site of future portal structure.

Initial work trailers and generators on-site.

Graham Sutton with skeleton of portal entrance structure at our warehouse in Golden.

Completed portal structure is ready to go to the mine!

Portal Structure installed at the new adit.

The new adit with rock bolts and mesh in place.

Newly-installed electrical panel (and a canine friend).

Detroit City Mine Adit in September 2017.

Looking down valley from the portal area.

Equipment and work trailer at mine site, September 2017.

Detroit City adit mining progress with freshly shotcrete-covered surfaces for stability control.

Tying in detonation cord and fuses before a blast at the Detroit City Mine.

An encouraging sign- the first specimen showing rhodochrosite encountered in driving the new Detroit City adit!

-Detroit City Project F.A.Q’s-

  • Question: Is this going to be a re-opening of the Sweet Home mine?

Answer: No. The Detroit City mine is a completely different mine, put in ‘from scratch’, and will not intersect or connect to any of the former Sweet Home mine workings. There are multiple reasons for this decision not to pursue mining rhodochrosite via the old Sweet Home workings.

  • Question: Are visitors welcome at the Detroit City mine?

 Answer: The mine is strictly off-limits to unauthorized visitors. At the present time, the mine is simply a tunnel into a mountain through unmineralized rock, so there really isn’t too much to see anyways. We will be posting frequent updates on the progress of the mine online (, Facebook, Instagram, and email updates), so stay tuned.

  • Question: Will Rhodochrosite and other minerals from the Detroit City mine look the same as those from the Sweet Home mine?

 Answer: While every pocket encountered at the Sweet Home mine was different and unique, we have strong reason to believe that the quality, color and size of rhodochrosite crystals found in the Detroit City mine will be similar to those found at the Sweet Home. That said, there is always the possibility that new types of crystallized rhodochrosite or other minerals will be found, and we are excited for that possibility. We would refer the reader to the special July-August 1998 issue of the Mineralogical Record magazine on the Sweet Home Mine to learn more about the mineralogy of this unique deposit.

  • Question: Aren’t you worried that new discoveries at the Detroit City mine could “flood the market” and drive down value and prices for fine rhodochrosite?

 Answer: Sweet Home mine rhodochrosite specimens have been highly valued in the mineral world for over 100 years. In 1929, well before minerals were valued the way they are today, Denver mineral dealer Arthur Pohndorf purchased a pocket of Sweet Home rhodochrosite crystals for $900, the price of a starter home at the time. The world-class color, size, and quality of Sweet Home rhodochrosite makes it among the most valued specimens of the mineral world and we are confident that the new supply of rhodochrosite crystals will be met with a strong demand, and will actually help grow the value of fine Sweet Home specimens already in private collections and museums.

Thanks for reading and stay tuned to and from more updates from the “Rhodo City”, Alma Colorado!