Helderberg Formation chert, Allegany County, Maryland.
Helderberg Chert comes from the Helderberg Formation. Bedded light colored chert from New Scotland Member. Bedded black chert reported from Licking Creek Limestone member. Sample collected from Flintsone, Allegany County, Maryland.
Helderberg Chert has a dull to waxy luster with colors ranging from cream, white, light gray, to bluish gray. It is often lightly mottled due to fossil content. Patina is lighter than interior color. There exist easily visible fossils including crinoids, brachiopods and conodonts. Cortex consists of a dull porous crust with calcite micro-crystals in surface.
Prepared By Ebright 1999
Updated October 22, 2016