My last posting, “Cryptic Message Leads to Brecciated Pierced Earrings!,” featured brecciated material from The Carver Agate Field. The posting promised more geological information.

And, here it is. Brecciated agates or other materials are ‘pieces held together with quartz,’ citing Gemstones of The World, by Walter Schumann, page 134. Sometimes the quartz that holds together the shards of broken rock can form agate between the shards.

Rock #4867

In this photo of Rock # 4867, there is a small fortification agate which can be seen between the shards. There is also a lava shard at the top of the photo.

Rock #4868

Rock #4868 displays jasper (dark brown horizontal strip near top) and agate shards (lower bottom right) as well as a brown lava shard (lower middle)

Rock #4833

Photo 4833 shows yellow/orange jasper shards cemented together by quartz which is mostly not visible except as a bluish material (lower right).

Rock #4993

Photo 4993 shows a hodgepodge of types and colors of shards of fractured material cemented together and also agatized (visible line on left side of stone).

Rock #5005

This photo of Rock 5005 shows shards of broken material (on right of photo) cemented together as banded agate (vertical white center). Black lines meeting at near 90 degrees are fractures ‘healed’ with quartz cementing broken pieces. We can see brown agate bands which have been broken, dislocated, and re-cemented.

Rock #4992

Photo of Rock 4992 clearly shows shards of broken material and the quartz that has cemented them back together. While the quartz is presently very hard and strong (much like a window pane), the quartz that originally cemented the shards together was likely a liquid or semi-liquid solution when it filled in-between the shards before hardening.

Rock #4580

Some geological observation can be made from the photos I have included. The angular nature of the shards indicates that various types of hard and relatively strong rock, e.g., jasper, lava, agate, were broken apart. I see this breaking occurring by either volcanic explosion from an eruption, and/or tectonic thrusting and lifting forces which occurred after the rock was initially formed. These forces dramatically cracked and broke rocks into small pieces and mixed together many various types of broken rocks.

Rock #4653

While lava rising within the earth can create a breaking force, I think that explosive forces were present in some cases in The Carver Agate Field. This explosive force is best explained by the various types of broken rock that are found cemented together. I also believe that the forces created and then shattered hard stone which was subsequently cemented together also reoccurred repeatedly, breaking and re-breaking breccia that had been cemented together. How many times these rocks were broken, re-cemented, and re-broken one cannot know. Certainly, the repeated processes of breaking, re-cementing, re-breaking, and then re-cementing has led to beautiful and interesting breccia that you see in these photos.

Over what period of time the volcanic forces occurred and re-occurred is uncertain. However, I have spoken with geologists who put the timing of volcanism in the Alpine, Texas area at over 25 million years ago. Please keep in mind that it is certain that there was not a single volcanic event, but rather multiple volcanic events over an unknown period of time and with unknown frequency. In my judgment, it is these repeated volcanic events that have made The Carver Agate Field, in many ways, different and more diverse than other agate fields that may have experienced fewer volcanic episodes.