Does anyone know what causes these holes?

See these? These are rocks that I find down around our little house in the woods. Our driveway is "paved" in quarried rocks and once in a while these holey rocks turn up.

Here's how my holey rock fetish started:
I was going through a painful divorce and hanging out with Manchild in the woods was soul soothing. Being a city girl, I was used to blowing and going all the time and down there, that just doesn't happen. Everything stands still. And quiet.

Anyway, being the sufferer of ADD/ADHD/PMS/LOCO/PETA/MADD, etc., I got pretty antsy doing nothing. I've always liked rocks so I started walking the driveway looking for pretty rocks to pass the time. I found a rock with a hole in it and I thought it was very interesting. The hole was perfectly round (not like the ones in the pictures I'm showing you). At the time, I was begging my maker to give me a sign that divorcing was the right thing for me to do and I told myself that if I found another holey rock it meant I was on the right path. I found 2 more.

It became a habit for me to ask the great maker questions and leave it up to the discovery - or not of more holey rocks to determine the answer. Now let me point out that I've spent my life walking with my head down looking at rocks, so I'd know it if I had seen these holey rocks before which I hadn't. I've been looking for them for about 4 years and I have about 100 of them in various sizes. I even had a friend make a necklace out of one of them.

So, have you ever seen anything like this? Does anyone know what makes the holes?
The area where these rocks were quarried is in eastern Texas. Here's a map so you can see:

That area was home to the Caddo Indians and some of the rocks look like they could have been turned into a bead. Others are way too natural to have been drilled by human hands. Most of the rocks are sort of sandy feeling, ie: they aren't smooth and shiny. 99% of them are tan colored.

This mystery is driving me crazy. I sure hope someone out there knows what made the holes. I'll keep looking for them but I just want to know WHY???