These are decommissioned Alexandrite laser rods (Cr:Chrysoberyl). These all lived out a full career in powerful infrared lasers but eventually failed--this can come from something as simple as a speck of dust landing on the end while they are lasing. They all have damage to the ends ranging from pits to deep chips, and some also show tiny internal butterfly fractures.
These are super cool artifacts but are also make exceptional gems when faceted!
These laser rods were meant for use in solid state lasers. They would have had light pumped into them from the side, either by a lamp or by another laser, absorbed that energy and converted it into the powerful coherent beam that lasers are known for.
Alexandrite is a somewhat uncommon lasing material. Aside from titanium sapphire eating into its market share over time, alexandrite's difficult and expensive growth has relegated it to niche applications, but where it is needed it really shines. And as a gemstone it is also stunning, with a strong color change, incredibly strong red fluorescence and trichroism, with three different color axes!
