Tyrkal

Tyrkal is a naturally-stable form of zenostium 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 during the many generations under Doisac's nuclear winter and constant tribal warfare. The original word has some similarities with the reconstructed 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. As tribes in many regions of the war-torn world regressed and forgot what they had once known, turning back to superstition, they would call the mineral by many names, including "wonder-stones" or "witching-stones", and used it in their shamanistic rituals. Yet those that retained some of their old knowledge and basic industry continued to leverage it in their weapons and vehicles, though on a much more modest scale than the imperial war-forges their forefathers had used to bring ruin upon their world.

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 electrical current. 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.

While inferior to industrially-produced zenostium nanolattices, tyrkal is also much easier to acquire and work with. Because most tyrkal crystals are natural, they exhibit impurities that dilute their unique abilities. As a result, pure tyrkal is highly sought-after by the Jiralhanae.

Acquisition
Tyrkal crystals require extremely high pressures and dense heavy metal concentrations to form. Both of these prerequisites are found on Doisac, although even here, only large earthquakes can create them. These are then ferried up to the surface on low-temperature magma channels. Mining them is delicate work, as their deposits must be kept at a cool-enough temperature to prevent them from evaporating. Most of the most accessible sources were depleted prior to the First Immolation, and the subsequent thermonuclear exchange destroyed the rest, making it extremely rare afterwards. However, the usage of excavation beams during the Jiralhanae-Covenant War of Conversion in the 2490s has unearthed new massive deposits of the crystals, allowing for tyrkal mining to become an extremely-lucrative industry once more.

Tyrkal-analogue minerals have been unearthed on a handful of other high-gravity worlds, but all of those found so far have been vastly inferior to the crystals found on Doisac and virtually unsuited for practical use. It appears that the material requires highly specific conditions and material composition to be useful or to remain metastable for any length of time. Since the Covenant found Doisac and the potential of tyrkal, they would make use of Jiralhanae miners on the most promising Doisac-analog worlds with tyrkaline deposits.

Production of synthetic tyrkal is possible through immense forges that replicate the conditions that are key to their formation, though the process is generally considered energy-intensive. The Jiralhanae once made extensive use of such techniques, but knowledge of this has been lost in the years after they nuked themselves back to a tier-6 civilization.

Usage
Jiralhanae technology is built around the exploitation of tyrkal. The crystals are a critical component of their native weaponry, with Spikers, gravity hammers, and even artillery shells all making use of it. They are extensively used in industry, usually in processes that require extreme pressures with surgical precision, although they can be used to limit the effects of Doisac's high gravity. Many early aircraft and spacecraft made use of tyrkal plates to support them in Doisac's crushing gravity, though they still usually had to use conventional means of propulsion to move. Even many large wheeled or tracked vehicles were equipped with tyrkal-based gravitic engines to support their enormous bulk.

In the Covenant, these crystals were usually used in the production of energy-efficient artificial gravity plating.