Blue Banded Dendritic Agate Report

The ‘deep pit’ on The Carver agate field ‘popped’ a 7+ pound,  6 1/2″ x  3 3/4″ banded blue agate beauty!

While the ‘deep pit’ photo gallery on this website has lots of photos of ‘deep pit’ beauties, this specimen contains a large yellow inclusion (on the left side of the photo) which has a blackish dendritic agate formation in and on its surface.  A dendritic agate is a tree-like or fern-like image.  The word dendrite is Greek for “tree-like.”  Normally, these dendritic formations found in specimens located on The Carver have formed on the outside surfaces of a geode or nodule, as shown below in photo 2849.    What is geologically odd here is that this dendrite formed on the yellow material which broke off, fell into the gas bubble pocket, which was then encased inside the larger blue agate when it later formed.

I believe that the dendritic formation inside the banded blue agate involved eight separate steps as follows:

1. molten lava with gases contained within it formed a large, approximately 6 x 4 inch, gas bubble

2. the molten lava cooled with the gas bubble remaining as a void or hollow in the lava

3. in or near the bubble, the yellow material formed as shown in the blue agate photos (4072 – 4081)

4. the dendrite (tree-like shape) formed in and on an exterior surface of the yellow material

5. the yellow material with the dendrite on its surface broke off and fell into the gas bubble pocket

6. a silica/water solution and mineralization (adding coloration) enters the gas bubble and forms the blue bands

7. as the silica material becomes less plentiful, it forms euhedral (euhedral crystals are those that are well-formed, with sharp, easily recognized faces) quartz crystals which fill in the center of the gas bubble, as shown on the right side of photo 4080

8. the silica banding and euhedral crystals encapsulate the yellow material with dendrite

Over countless eons, this large blue banded agate has eroded out of the lava in which it formed.  This is because lava is much softer and less weather resistant than the silica of which the large blue nodule is formed.   Midland, Texas geologist Bill Halepeska has opined that the large blue nodule was formed as part of the Paisano volcano on the west side of Alpine, Texas.   It is his belief that after this large nodule weathered out of the lava which had encased it, it was picked up and carried for several miles by a mud flow of volcanic materials, which then deposited it in the ‘deep pit’.  For this reason, the ‘deep pit’ materials shown on this website and this large blue banded agate appear to have been formed from a different volcanic formation which formed all of the other rocks from The Carver shown on this website.  And it is for this reason that the ‘deep pit’ materials have very different characteristics from all of the other rocks found on The Carver.  The Carver is, therefore, the result of two different volcanic systems.  More information about the ‘deep pit’ origins will be forthcoming at a future date.

Click on the photos to enlarge them!


The Deep Pit Galleries contain many other specimens, so be sure to check them out:

The Deep Pit Agate, Amethyst, and Smoky Quartz Geodes Galleries