Gold Deposits at the Zortman-Landusky Mine

This page was written by Erin Klauk as part of the DLESE Community Services Project: Integrating Research in Education.

Gold is one of the most economically important metals produced. As of 1991, more than 83% of gold consumption went into jewelry, 6% was used for medals and official coins, 6% was used in electronic equipment, 2.2% was used for dental materials, and 2.8% was consumed in a variety of industrial applications. These markets support an annual gold production of about 2,200 tons worth almost $25 billion ([Kesler, 1994] ).

There are many types of gold deposits (more info) including vein deposits, contact deposits, replacement deposits, disseminated ore and placers. A few miles south of the Fort Belknap Indian Reservation lies the Zortman-Landusky mine where gold is found in intrusion related breccia-hosted deposits in the Little Rocky Mountains. In this type of deposit, gold mineralization is found in magmatic-hydrothermal or phreatomagmatic pipe-like breccias (Figure 1) associated with the intrusion of stocks, plugs, sills or dikes into a wide variety of host rocks ranging in age from Precambrian to Tertiary (Mineral Commodity Report 14: Gold (more info) ).

During the Tertiary, igneous activity domed the Little Rocky Mountains and formed the laccolithic intrusion, dikes and sills where gold-silver mineralization occurred. The gold is found in small quartz veins that are concentrated in large fissure zones of shattered and altered rock. Some low-grade gold is also present in auriferous pyrite disseminated locally in the syenite and other intrusive rocks. In a few areas gold occurs in higher-grade replacement deposits in limestone (Status of Mineral Resource Information for the Fort Belknap Indian Reservation, Montana ( This site may be offline. ) ).

To further investigate gold deposits at the Zortman-Landusky mine, follow the links below.

Gold, 6.8 cm high, Homestake Mine, Salmon River District, Siskiyou County. Details

Gold Deposits

Resources containing information on gold deposits.

Gold Deposits at the Zortman-Landusky Mine

Resources containing information on the gold deposits at the Zortman-Landusky mine.

For ideas on how to use these webpages in a classroom, a Study Guide is provided.