BIPOLAR FLAKING is something you can do with pebbles of materials that are sometimes difficult to break into. Quarzites can be tough, but there's generally enough of it around when you come across it in a river bed or on its terraces. Coastal San Diego is such a region. Eastern Asia is another.
Given the lack of control regarding by-products, the knapper's primarily concern is generating a solid, centered strike on top of the core. With a four-inch quartzite pebble you can get a four-inch edge, a very difficult thing to do using direct percussion.
Sometimes the core buckles under the first hit, usually it takes several hits. Any more than that and you may start to consider a larger hammer or maul.
Only a few cores have been selected in order to introduce the kind of variability that can occur during this process. Included here are three quartzite examples, one of felsite, and the other of a poorly cemented mudstone. This section will gradually be appended to include other types of source materials, especially flints and other cryptocrystallines.
Quartzite Bipolar Core 1
Quartzite Bipolar Core 2
Quartzite Bipolar Core 3
Felsite Bipolar Core 4
"Mudstone" Bipolar Core 5