Synthetic gold crystals
Looking more polished in shape and lustre than the usual patina on natural native gold that we share every now and again (seehttps://www.facebook.com/TheEarthStory/posts/618216978239350), these 99.99% pure crystals were grown by chemical vapour deposition (a method also used to synthesise diamonds) using chlorine gas to transport the gold atoms. In nature, gold deposits are usually leached, transported and deposited in varied compositions of hydrothermal fluids, being deposited when conditions such as oxidation/reduction or temperature change. Here too the gold atoms are often transported in solution as ligand complexes with chlorine and other halogen elements.
Image credit: Alchemist-hp