Search results
Results from the WOW.Com Content Network
The name is derived from the Nahuatl language and means "hand-wood". [2] Its sides are embedded with prismatic blades traditionally made from obsidian, which is capable of producing an edge sharper than high quality steel razor blades. The macuahuitl was a standard close combat weapon.
This human-made material, when scraped with any hard, sharp edge, produces sparks that are much hotter than obtained with natural flint and steel, allowing use of a wider range of tinders. Because it can produce sparks when wet and can start fires when used correctly, ferrocerium is commonly included in survival kits. Ferrocerium is used in ...
For example, concretions in sandstones or shales are commonly formed of a carbonate mineral such as calcite; those in limestones are commonly an amorphous or microcrystalline form of silica such as chert, flint, or jasper; while those in black shale may be composed of pyrite. [18]
Alternative natural materials are natural materials like rock or adobe that are not as commonly used as materials such as wood or iron. Alternative natural materials have many practical uses in areas such as sustainable architecture and engineering. The main purpose of using such materials is to minimize the negative effects that built ...
It is usually mixed with oil, sometimes water, and rubbed on the surface of varnished or lacquered wood with a felt pad or cloth. Rotten stone is sometimes used to buff stains out of wood. Some polishing waxes contain powdered rotten stone in a paste substrate. For larger polishing jobs, rotten stone mixed with a binder is applied to polishing ...
[19] [20] [21] While this has been shown to work, archaeologists have yet to discover an actual spoon made of magnetite in a Han tomb. [ 22 ] Based on his discovery of an Olmec artifact (a shaped and grooved magnetic bar) in North America, astronomer John Carlson suggests that lodestone may have been used by the Olmec more than a thousand years ...
Jet is a product of decomposition of wood from millions of years ago, commonly the wood of trees of the family Araucariaceae. [5] Jet is found in two forms, hard and soft. [5] Hard jet is the result of carbon compression and salt water; soft jet may be the result of carbon compression and fresh water. [5]
Most gold is mined as native metal and can be found as nuggets, veins or wires of gold in a rock matrix, or fine grains of gold, mixed in with sediments or bound within rock. The iconic image of gold mining for many is gold panning, which is a method of separating flakes and nuggets of pure gold from river sediments due to their great density ...