Are the Boley chert breccia clasts truly agate? Neil Suneson, William Lyon and David Goza di erentiated the chert pebbles and cobbles found in the Boley Conglomerate as follows.

Chert Breccia A.

Subclasts are unconnected and appear to be unrelated to each other. Subclasts vary from rounded to angular, and they vary from pebble to grain-sized. In a sedimentary sense, the subclasts are moved far enough away from each other and separated by enough cement that cannot be reconnected.

B.

Stratified chert in which no delamination or brecciation has occurred. Small fossil fragments are present in some specimens; sponge spicules appear to be the most common.

C.

Slightly delaminated stratified breccias are a type of autoclastic breccia in which the original rock is sedimentary and the subclasts have delaminated largely along bedding planes.

Stratified Chert A.

Massive or unstratified chert. Clasts are typically pebble-size in the Boley Conglomerate that likely originated as a thickly stratified sedimentary rock.

B.

Stratified chert in which no delamination or brecciation has occurred. Small fossil fragments are present in some specimens; sponge spicules appear to be the most common.

Banded Chert

The banded agates are rare specimens with fracturefills or void space fillings in which the silica is banded like agate. The banded silica filling can constitute either a minor portion of the rock or most of it. The bands are not related to the original stratification. They represent repeated precipitation.