Expedition Research 2023

Obsidian is a relatively rare volcanic glass that can be fashioned into a thin, sharp blade. I acquired a 1"x2.5"x 3.5" chunk from a roadside rock and mineral shop in Alaska in April 2021.

Apparently, ya just methodically chip away at the obsidian chunk with a stone until the desired shape is obtained. It can't be that hard to do if ancient cave people did it! Enjoy these interwebs facts about what some esteemed individuals (such as myself) refer to as "the pre-steel scalpel":

Obsidian is a form of volcanic glass produced by rhyolitic volcanism.

Obsidian is a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth

Although obsidian is a comparatively rare material, its excellent flaking properties have resulted in it being widely distributed.

Obsidian has been used across history to make weapons, implements, tools, ornaments, and mirrors. Because of its conchoidal fracture (smooth curved surfaces and sharp edges), the sharpest stone artifacts were fashioned from obsidian. Native Americans and many other peoples, including those of the ancient Aztec and Greek civilizations, used obsidian.

Source:

Britannica, The Editors of Encyclopaedia. "obsidian". Encyclopedia Britannica, 19 Nov. 2022, https://www.britannica.com/science/obsidian. Accessed 7 January 2023.

Obsidian consists of about 70 percent or more non-crystallized silica (silicon dioxide). It is chemically similar to granite and rhyolite, which also were originally molten. Because obsidian is not comprised of mineral crystals, technically obsidian is not a true "rock." It is really a congealed liquid with minor amounts of microscopic mineral crystals and rock impurities. Obsidian is relatively soft with a typical hardness of 5 to 5.5 on the mineral hardness scale. In comparison, quartz (crystallized silicon dioxide) has a hardness of 7.0.

Source:

https://volcano.oregonstate.edu/volcanic-minerals/obsidian

More to come on obsidian found in Yellowstone, but for now I'll leave you with this:

• Obsidian Cliff is the primary source of obsidian in a large concentration of Midwestern sites, including about 90% of obsidian found in Hopewell mortuary sites in the Ohio River Valley (about 1,850–1,750 years ago).

https://www.nps.gov/yell/learn/historyculture/obsidiancliff.htm