Jaspillite

Jaspillite, or jaspilite, is a chemical rock formed similar to chert. It is usually iron rich. It also has the name jasper taconite. 

Jaspillite is typically a layered mixture of hematite and quartz. It is common in the banded iron formation rocks of Proterozoic and Archaean age in the Canadian shield of North America.

Jaspillite is also a sedimentary rock.in certain lead-zinc ore deposits.

It is used as a gemstone.Gemstones of North America - Volume 1, John Sinkankas - 1959 p.345

 References 

 Other websites 
Mindat.org data

Category:Sedimentary rocks
Category:Gemstones