The rocks around you here are covered in miarolitic cavities. Miarolitic cavities (or miarolitic texture) are irregular shaped cavities or holes most commonly found in granitic rocks, but are also found in a variety of igneous rocks.
These cavities can vary in size from a small pinpoint to as large as a soccer ball. Most often they will be roughly the size of a golf ball or a hen’s egg. Quite often the inside of the cavities will be lined with tiny crystals.
They form when magma is force up into exiting rock underground. When this molten rock becomes trapped the gases begin to escape and create cavities or bubbles. In the other words, the molten rock boils while still trapped below ground level. Once this magma hardens into rock the bubbles are locked in the strata.
Later, while the rock is still below ground geothermal activity may push hot mineral-rich water into the cavities and crystals will grow within them. Due to this miarolitic cavities can be sources of rare and unusual minerals.
Erosion will then bring the rock to the surface where they cavities are exposed. Some will appear as bulges in the rock. Others will be small dents or ‘cavities’ on the rock surface. If you look closely at and feel inside the ones in this area you will notice that some have small crystals lining their sides.
Miarolitic cavities are common in the Wichita Mountains but not in the number and variety seen here. Some may contain colorless and smoky quartz. As you hike and cache throughout the Wichita Mountains keep your eyes open for more of these cavities.
To receive credit for this cache, email me the answers to the following questions.
1. On average how large are the cavities?
2. On average about how many cavities are there in one square yard or one square meter?
3. About how long and how wide of an area is covered in cavities in this one formation?
Congratulation to 2Moore on the FTF.
Another Quality Clan Hide