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Contact: sergey606@gmail.com

Please join us for the Elko GSN Holiday Party

Thursday, December 18, 2025

Western Folklife Center, 501 Railroad St., Elko, NV

Drinks and Appetizers at 6 pm; Talk at 7 pm

OUR HOLIDAY FOOD & DRINK CO-SPONSORED BY:

BOART LONGYEAR & LEGARZA!

SPEAKER: Rick Streiff

TITLE: The Silver Valley: “Still Poorly understood after all these years”

(Abstract & Speaker Bio below)

Happy Holidays from the Elko Chapter of the Geological Society of Nevada. Many thanks go to all who have helped it be a successful year of geologizing here in Elko! All of our sponsors, speakers, and picnic masters, you are all pretty fantastic folks and are appreciated.

On Thursday, December 18^th, head on down to the Western Folklife Center to bid on your favorite item(s) in the silent auction and enjoy a meal plus our speaker Rick Streiff. The festivities will begin at 6:00 PM – dinner at 7:00 PM. While you are enjoying the holiday spirit, don’t forget to thank our generous sponsors for the food, and merriment: Boart Longyear and Legarza are always quite generous for our holiday spirit(s) and we are grateful for them!

Re: the silent auction: If you have any donations to be made for the silent auction in Elko, please drop them off anytime during business hours at Rangefront Mining Services in Elko, on Railroad Street. When items are dropped off at Rangefront, please fill in your information and item description on the donation list for our reference! This will assist us in being sure no items are displaced. Thank you everyone and have a very happy holiday season.

If you have any questions, please contact GSN Elko Chapter President, Sergey Konyshev (sergey606@gmail.com).

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Abstract: The Coeur D’Alene district in northern Idaho has been producing silver and base metal ores for over 120 years. The district is one of the largest silver producing areas in the world, producing over 1.25 billion ounces. Despite this long history, the district geology is still not well understood. There is debate over the age of the deposits, structural history and controls as well as genesis of the ore deposits. The district remains poorly documented with a lot of contrasting and conflicting information as well as urban legends.

Recent work in the district has highlighted age constraints on mineralization. Regional work on the Rocky Mountain thrust and fold belt as well as the Basin Supergroup rocks points towards a late Cretaceous to Paleocene age of mineralization associated with the 800-kilometer transpressional Lewis and Clark Line (LCL). This age is consistent with mapped crosscutting features in the district. 

Mapping has also highlighted four distinct periods of deformation. D1 consists of Laramide age regional folding. D2 is sinistral transpression along the LCL which developed the ductile to semi-ductile fault zones hosting mineralization. D3 deformation is a post-mineral compressional event which formed parasitic folds and deformed the veins. The final deformation event (D4) is recent dextral brittle faulting, highlighted by the Osburn fault which has bisected and offset the district by roughly 16 kilometers. The two later deformation events have offset the stratigraphy after mineralization and caused confusion over relative fault movements in the district. There has been a long debate over the genesis of mineralization. The district likely represents a Polymetallic Orogenic district with characteristics similar to many Orogenic gold systems.

The Galena mine has been operating for almost 140 years and yet is one of the shallower mines in the district. There are currently 76 named veins in the Galena Complex and many more unnamed veins. New veins continue to be discovered, including four in 2025. There are two structural styles of veining hosting two distinct styles of mineralization. Ductile to semi-ductile E-W sinistral faults generally host Pb-Ag veins while NE striking extensional veins usually host Cu-Ag mineralization. The principal silver mineral in the Cu-Ag veins is tetrahedrite, which also contains significant antimony. Since 2000, the Galena complex has produced over 20 million pounds of antimony.

Biography of Rick Streiff, Certified Professional Geologist: Rick Streiff graduated with a BS in Geology from the University of Oregon and has been working in the mineral industry for more than 50 years. He worked at several porphyry related Intermediate Sulfidation Epithermal systems in the Cascade Range of Oregon early in his career. He worked for 10 years with Echo Bay Mines at Round Mountain, McCoy-Cove and finally at Kettle River, Washington. He then worked for 18 years with Newmont, mainly in Nevada at various sites including Deep Post, Midas, Twin Creeks, and up and down the Carlin Trend. In addition to various Chief Geologist roles, he was Newmont’s Underground Geology Manager for Nevada as well as the Carlin Trend Surface Geology Manager.  He spent 4 years at Waihi, New Zealand with Newmont exploring the Hauraki Goldfield and the Taupo Volcanic Zone before returning to Nevada and retiring. He later went back to New Zealand for OceanaGold. His team discovered the Rex low sulfidation vein in Waihi plus the greenfield WKP discovery, a high-grade low sulfidation vein system which remains open along strike and is still being drilled today. Rick spent 5 years consulting for various gold companies where he specialized in low and intermediate sulfidation epithermal systems. He came out of retirement a second time and is the current Executive Vice President of Geology for Americas Gold and Silver, where he is focused on exploration and operational improvements at both the Galena Complex in Idaho and the Cosala operation in Sinaloa, Mexico.