Alchemy Symbols
Alchemical symbols, originally devised as part of the protoscience of alchemy, were used to denote some elements and some compounds until the 18th century. Note that while notation like this was mostly standardized, style and symbol varied between alchemists, so this page of alchemy symbols lists the most common.

The art of alchemy was handed down through the centuries from Egypt and Arabia to Greece and Rome, and finally to western and central Europe. The word is derived from the Arabian phrase “al-kimia,” which refers to the preparation of the Stone or Elixir by the Egyptians. The Arabic root “kimia” comes from the Coptic “khem” which alluded to the fertile black soil of the Nile delta.
Here are some of the most common alchemy symbols:

Diamond

The Four Basic Elements
Symbol for Fire
Symbol for Water
Symbol for Earth
Symbol for Air