Some natural resources have found use by humans as tools and utensils requiring somewhat minimal “reworking.” I’m positive that there are many more examples than are given below.
Agate (silicon dioxide, a variety of chalcedony quartz). Used to make mortar-and-pestles, leather burnishing tools, and precision balances.
Bamboo (Bambusoideae subfamily). Oh, so many useful things made from the hundreds of varieties of bamboo. Houses, weapons, water pipes, musical instruments, to name but a few.
Bone. Animal bones have been used since the dawn of mankind to make tools like needles, arrowheads, buttons, and axes, to name a few. Bone is also an important ingredient in bone china (a type of pottery).
Calabash (Calabash tree, Crescentia cujete, and calabash vine, Lagenaria siceraria). A large gourd with a very hard rind that is hollowed out and used as a container.
Clay. Clay comes in a wide variety of chemical compositions, each with different properties and uses, from fire clay (used to make high-temperature utensils like crucibles), to the common clays used for earthenware pottery, to meerschaum (used for making the famous meerschaum pipes).
Coconut (Cocos nucifera). The hard shell of the seed is used as a container and to make tools.
Flint. A type of sedimentary quartz with a cryptocrystalline structure that can be knapped (chipped) into very sharp edges and points (i.e., cutting, scraping or chopping tools, spears and arrowheads).
Jade. The term actually refers to two different minerals with very similar properties and uses: jadeite and nephrite jade. Both are very hard minerals used to make tools and weapons.
Loofah (Loofa, Luffa aegyptiaca). A loofah is a sponge made by leaving the mature fruit of the loofa vine out to dry, until only the fibrous skeleton remains.
Millstone (Burrstone). Burrstone is a type of siliceo-calcareous stone whose dressed surface is rough, sharp and hard and makes for great grindstones for milling wheat and other grains.
Obsidian. Also known as volcanic glass, obsidian is formed when high-silica lava is cooled very quickly. It can be knapped into a cutting edge sharper than the sharpest steel edge. Obsidian has been used as a tool by humans, almost since the dawn of humanity.
Quill (or spine). Feather quills have been used as pens, and porcupine quills (technically a “spine”) have been used as needles and weapons points. For obvious reasons.
Reed (common reed, giant reed). Like bamboo, the hollow, rigid stems of reeds have found many uses.
Shell. “Shell” in the context of tools most often refers to the hard calcium carbonate-based exoskeleton of marine invertebrates.
Sponge (Spongia spp.) Sponges are a genus of marine animals whose soft, porous, fibrous skeletons have a long history of use as tools by humans. Sponges were harvested nearly to the point of extinction, so natural sponges are rare these days.
Whetstones. Whetstones are used for grinding the cutting edge of a (usually metal) tool in order to sharpen it. Natural whetstones include such stones as novaculite, also called Turkey stone or Arkansas stone (a cryptocrystalline silica similar to chert or flint), and Japanese wetstones.
From the Crazy Useful Catalog:
Crazy Useful Things
A Dictionary of Natural Resources and Their Products