Ruby Fragments are materials required for the crafting of Elixirs and Incense by the Alchemist. They can be collected from glittering ore veins dotted around the world, also as loot from World Bosses and caches rewarded for completing Whispers of the Dead. They also drop from random Elite kills in Helltides.
They can be upgraded at the Jeweler into gems to socket into items.
The other types of Fragments you can find are: