"Flint" is simply another word for darker colored "Chert", and was formed from deep sea silica deposits during the late cretaceous period (60-95 million years ago). It provides the hardest surface and is the primary stone used for creating sparks for fire-starting.
"Chert" (microcrystalline quartz) (SiO2) includes chalcedony, agate, jasper, and flint. Chert and flint are so similar that there is no sharp distinction between them. Dark-colored nodules are called flint, and the light-colored variety is called chert. The variation may be due to the inclusion of variable amounts of organic matter during formation. Other chert colors can include pink, brown, and purple. Texas Chert has a conchoidal fracture, a hardness of around 7, a dull luster, and a colorless streak. Arrowheads in Texas and elsewhere were commonly crafted from chert.
The irregular masses of chert that are common in Texas limestone were formed by silica-rich groundwater passing through the sediments before they were lithified (formed into rocks). These irregular masses, known as nodules, often have exotic shapes uninfluenced by the textures in the host limestone.
Georgetown flint (sometimes called Georgetown Blue flint) is the name given to an unusually good chert variety that occurs along the eastern fringe of the Edwards Plateau, near Georgetown, Texas.
Georgetown comes in several shades of gray, with four distinct 'flavors' present in the quarry. The best of these is a 'steel' gray that is glassy, translucent, brittle, and rivals any natural siliceous stone in North America in flaking quality. In our quarry, flint occurs in three forms: 1) as ledge flint, in seams or bands approx. 4 to 20 centimeters thick, 2) as bands of discontinuous thin, flat cobbles (4 - 10 centimeters thick-perfect for making bifaces), and 3) as rounded nodules up to about 30 centimeters in diameter. Some Georgetown flint can be improved by heat treating, but the material is perfect for knapping just the way it is and is the hardest found in nature.
Most of our flint materials are known as Georgetown and/or Central Texas Flint (Chert) and these are among the hardest flint known, which made them popular for Indian arrowheads and spear points. It is found mainly just below the ground surface and has been exposed to the elements which gives it superior hardness and strength. We clean the material by hand and remove most of the algae growth but we are not aggressive as that may damage the stone.
We also have local versions of Keo-Kuk white flint (chert) that is commonly found in Oklahoma but also in the Texas Hill Country where we are located. This is a high-quality, creamy white flint that may or may not have orange-colored "lightning" streaks through it. And, we do have limited quantities of what is known as Indian Jasper in our fields. This is a very hard stone that is good for arrowheads, spear points and it does spark well for use as a firestarter.
None of our flint has been fire-treated, unless it was done by nature. Fire-treating (heat treating) is sometimes done to improve the hardness of the flint, but this is not necessary for Central Texas Flint or Chert.
The Term "Flint", when used in the practice of flintknapping, actually refers to a wide variety of items including true flint, chert, obsidian, jasper, quartzite and other stones that are brittle and have a fine-grained, smooth texture.
At Texas Flints we provide primarily true flint (grayish or brownish coloring) and/or chert (light colored stonelike material). However we also have hard rock that can be formed to make arrow heads, spear heads, clubs, axe heads and other tools.