Tyrkal

Tyrkal is a naturally-stable form of nilatite used to generate artificial gravity. It is found in large quantities on the Jiralhanae homeworld of Doisac.

Etymology
The origins for the material's name is believed to be connected to the old Jiralhanae word "Yrrokall", which apparently means "rising rock" or "lifting stone". Over time, the "Yr" sound morphed into "tir/tyr" over generations as different groups mixed together, the word overall got streamlined and lost the "o", while "kall" lost the long consonant as the language became harsher and more crude due to the nuclear winter and tribal warfare. The original word has some similarities with the root name of the species, Yrrolhanag, suggesting some sort of connection between the two.

Today, the most Jiralhanae use "tyrkal" without any regard for or knowledge of the word's etymology. The less developed tribes call them "wonder-stones" or "witching-stones", as they saw a lot of ritual uses during the dark ages.

Tyrkal has a number of alternative names. The UNSC officially calls it Substance-16, but has also referred to it as Exotic Doisac Elements or EDEs.

Characteristics
A yellow metamaterial crystal made from carbon and heavy metals, tyrkal has been compared to doped diamonds, but with the ability to levitate if subjected to a high-frequency alternating-current electricity. It does this by imparting motion without a reaction force, with these qualities more easily observed within a powerful gravitational field. Tyrkal is extremely sensitive to oxygen atmospheres, and will burn up at fairly low temperatures. This characteristic is why the UNSC recovered few of the crystals during the Human-Covenant War.