Varies widely. The arrow heads are probably about 100 AD to 1500 AD and the Spear points from 100 AD back to 7500 BC. Documented mammoth kills near my place set a post ice age bookend on some of the spear points. 12th century US was tough on native populations as I have studied....so I am speculating on native arrowhead dating, although I have a large reference library the I use as a basis for my approximate dating.
The knives are anybody's guess, IMO, although two of them I found were in proximity to what I believe was a Caddoan culture site I stumbled across.
There is a lot of local native pottery shards/pieces, some with various striations/ornamental markings but a lot of simply reduced fired, unmarked pieces are prevalent. I found a site out at Lake Somerville right after the lake was built....in about a foot of water, I literally stubbed my toe on a metate.
Lots of scrapers, suspected atl weights, shaft scrapers, and large, sharp chert pieces appropriate for breaking open bones for marrow, too. Petrified deer antler 'picks', bison teeth, shell middens, and massive cooking areas covering acres where natives grilled fresh water mussels on burning coals along the Little River abound. This area was teaming with native life for centuries before our ancestors came along.
When the fire ants showed up, they wiped out the indigenous population of pocket gophers....in the sandy hills along the Brazos, the pocket gophers literally left goppher mounds in every square foot of loamy/sandy soil, constantly churning up artifacts to the surface, where the next good rain would reveal them to those looking. Stories from old timers coming out to the hill I live on included stints with their sons and 5 gallon buckets, picking up hundreds of arrowheads back in the 50's and 60's after passing rains. I only caught the last 5 or 6 years of the pocket gopher 'era' when I moved out here before they disappeared, and that was when I first took an interest in the native population and culture. Back then, I found it difficult to learn any real facts outside of a rare few books such as Suhm and Jelks as rough dating guides and info from Thomas Hester. I didn't even know A&M housed Harry Shafer, a local expert at TAMU, until years after my interest began.
Those days of the gopher mounds are gone, but I am aware of over 100 sites in Brazos and Burleson county where roads, development, and construction have revealed sites of all ages.
I never dig for artifacts. If others do, I will look (I am not referring to archeological digs but instead, unrelated human disturbances), but that is just my personal rule. I stick to my land these days to hunt, but in the past, I would look in road cuts and gravel pits and such, where I had permission.
[This message has been edited by Yuccadoo (edited 7/9/2010 5:38a).]