Reposted Sep 29, 2024
Many people learned about organic compounds (made of C, H, O, N, etc.) in high school chemistry. These compounds have a specific chemical formula, and a structure often depicted by letters and lines to represent the chemical bonds.
Metals can be combined in many different mixtures, called alloys. This is more like a baker mixing ingredients for the desired result. Most alloys have from two to four main components. Most have tiny percentages of a number of other elements that were in the original ore and would be expensive to remove.
Here are diagrams showing some alloys.
Pure compounds are never pure, but the percentage of impurities may be very low.
Cermics have a crystalline structure with a fixed ratio of one compound to another.
Alloys are mixes at the molecular level. There is a wider range of variability in the percentages of these mixes. However, some percentages are very common because they are easiest to process, typically eutectic mixtures where both elements melt at the same temperature. Non-eutectic alloys may need to be machined or cold forged, where as eutectic allows are more easily worked hot. There can be some range of mixes (i.e. grades of steel) that can be worked hot as long as they aren’t melted.
Argentium Silver – a non tarnishing silver that comes in 93.5% or 96% purity. Some of the copper is replaced with germainum to get the non-tarnishing effect.
Britannia Silver – 95.833% silver with the rest copper.
Spangold – a gold-copper allow that is heat treated to give a microcrystalline surface that has a multi-color crystal (spangled) surface.
Grey Gold – a gold and palladium mixture
Purple Gold (also called violet gold or amethyst gold) is a mix of gold and Aluminum that has a large percentage of AuAl2 crystals.
Blue Gold – gold mixed with gallium or indium. There is a second blue gold that is a surface treatment of oxidized iron and nickel
Black gold – a black surface is given by oxidizing the other elements mixed in with the gold. (black gold also refers to crude oil)
Corinthian bronze was highly valued in ancient times. It is unknown if it was an alloy of gold and copper, or simply very high grade bronze.
Crown gold – 22 karat gold introduced in the 1526 gold crown coin.
CuSil – 72% silver, 28% copper. A eutectic mixture used for vacuum brazing
Goloid – 87.3% silver, 3.6% gold, and 9.1% copper by weight.
Hepatizon (also called Black Corrinthian Bronze) was a black alloy in antiquity. It is thought to be an oxidized mixture of copper, with a bit of gold and silver that had a dark purplish patina.
Orichalcum or aurichalcum is mentioned in ancient texts, including Plato’s story of Atlantis. It was second in value to gold. There are various opinions on whether it was a noble metal like platinum or perhaps some grade of bronze or brass.
Osmiridium and iridosmine are natural alloys of the elements osmium and iridium, with traces of other platinum-group metals.
Black Rhodium is an allotrope of rhodium that is black and shiny. Sometimes used to coat jewelry.
Platinaire – 92.5% silver, 5% platinum and other elements. No nickel and thus hypoallergenic. Often made from recycled metal objects.
Platinum sterling – a variety of alloys of silver and platinum.
Potin – a base metal used in greek or celtic coins. A mix of copper, tin and lead.
Shakudo – a Japanese mix 4-10% gold, 90-96% copper. Can be processed to have a patina of black or sometimes indigo.
Shibuishi – a Japanese copper allow that can be patinad several shades of grey and muted green, brown, blue.
Titanium Gold – is a mix of titanium and gold. However many object that say Titanium and are gold colored are titanium nitride.
Tumbaga – various mixes of gold and copper found in pre-columbian Americas.
More interesting information about alloys can be found at: