I don't know....but it has to do with shape and the way they were chipped.
I'd look for another collector to tell you where to look. Flea markets Fairs and such are a likely place.
The link below may ( or may not!! LOL!) give you some info.
Linda C

Here is a link that might be useful: artifacts

There's probably a State agency of some sort that deals with items of archeological interest.

Tricia, in "Indian country" items that new are of little interest to anyone but collectors...
But....very often much older items are found in the same place....
A bend in the river was always a good place for a camp.
I know a man who hunts.....and has shelves and shelves of points and scrapers and such.....and he has found pieces that appear to be very early.....similar in style to Clovis points.
Linda C

Can you post some pics of your finds? That should would make the fun hobby of gardening even better! I know where I grew up there was a farmer's field that people would go to when he plowed because they'd find arrowheads. I've never found one :-(

Deb in PA

Wow, that surprises me. I'm always seeing "stuff" on Antiques Road Show that's Indian in nature and it's always worth a King's ransom, or so it seems.

I dig up shards in our garden infrequently. We've been here 2 growing seasons and have 3 shards. One is of an old flow blue cup of some sort. The other two are redware and I can't tell what they're from. They're in one of our display cabinets...our very own archeological treasures!

That reminds me...I've got these "things" that look for all the world like pre-Columbian artifacts. I've had several appraisers look at them and a couple thought several of them were the genuine article. I don't know what to do with them? I use them in my garden as "art"! I really must find someone knowledgeable and find out what those guys really are!

In my state I would take them to the state museum for an opinion. Is this feasible for you?