Indium

Indium is an element in the "poor metals" class (beyond the transition metals, before the nonmetals) of the periodic table. It is soft and silvery-white. It is stable in air and water, but dissolves in acids. It has a specific gravity of 7.310. It has two stable isotopes (actually one, but another one has a half-life of over 10¹⁴ years).

Indium
Properties
Atomic symbol	In
Atomic number	49
Classification	Poor Metals
Atomic mass	114.818 amu
Other Information
Date of discovery	1863
Name of discoverer	Ferdinand Reich and Hieronymous Richter
Name origin	From the indigo blue it shows in a spectroscope.
Uses	Used as a coating for high speed bearings, in high-quality mirrors, solar cells, nuclear power regulators, photo cells, thermistors, and transistors. Also employed in low-melting alloys for safety devices.
Obtained from	Found in some zinc ores, but is primarily produced as a by-product of lead and zinc smelting.

Indium was discovered spectroscopically spectroscope (many 19th century element discoveries were made this way) while searching for thallium in zinc ores.