A trap rock composed of hornblende and feldspar.

View pictures relating to mining at Wisconsin Historical Images.

Learn More

Dictionary of Wisconsin History

Explore more than 1,600 people, places and events in Wisconsin history.

[Source: "Glossary of Miners'&Mineral Terms" in St. John, John R. A True Description of the Lake Superior Country ... (New York, W. H. Graham, 1846).]