IS hard to figure out, Eric!
You are on the right track. The "illite" is a good example.
Here all this time I thought you were supposed to learn to "read the dirt" to find the rocks, now you're telling me I need to "read about the dirt" too! It never ends.
Here's some interesting reading for you if you haven't found this all ready;
https://pubs.usgs.gov/bul/1072d/report.pdfIt's a little old but a good report with lots of good info. The first page is good and then on the third or fourth page is the section
"Genesis of Quartz Crystals". The Bedrock and Quartz Veins and Weathering of Bedrock sections will help alot in trying to answer some of your questions.
While you are reading those sections, for comparison to the "Roost", those hard different colored layers we were calling "mudstone" is the host rock you are looking for now in the form of "Saprolite" mentioned in the report.
I'm really glad to see you trying to figure out all that geology. When you do you can let me in on it.
Eric, I won't be out this weekend, but am planning on being there the next. I want to continue my corner some but feel free to dig there in the meantime. There are a lot of good crystals in the top 2-3 feet right there.
Have Fun!