A magical crystal that can be found in the soil of the Mamono Realms and appears in the Monster Girl Encyclopedia World Guide II: Mamono Realm Traveller's Guide book.
Monster Girl Encyclopedia World Guide - Side II introduces a similar mamono realm ore called Druelite. Originally known as Gooze ore, they were crystals found in a cave in Lescatie, and capable of absorbing small amounts of mana from the air and emits a beautiful blue glow. The Gooze ores were otherwise useless, however, due to their low capacity which cause the crystals to shatter and wasted when touched by a human or monster. But after Lescatie became a mamono realm, the Gooze ores were changed by Druella's mamono mana and removed its limitations, as well as giving them ability to amplify absorbed mana; but the red glowing ores would now convert all of the stored essence into mamono mana as well.
Guide Book Entry
Monster Girl Encyclopedia World Guide II
One of the unique ores that can be mined underground in any mamono realm, they're even easier to imbue with magical energy than Mamono Realm Silver. Not only are they used as ornaments, the gems are also excellent as a material for magic items. The raw gems are transparent and colorless, but if imbued with essence or mamono mana, the color, brilliance, transparency and even shape of the crystals will variously change depending on the owner of the essence or mamono mana that's contained inside.
These changes are different depending on each individual, and one person’s energy cannot make exactly the same gem as another person. A gem is thus produced that is “unique to each person” and can only be made with that person's essence or mamono mana. For that reason it's even possible to distinguish an individual through these gems.
Furthermore, once a gem has had essence or mamono mana poured into it, it stores that energy, and this causes it to become fixed. This means that once a magic gem has been changed, it won't ever change again. Since, if it is accidentally imbued with magical energy and changed, a magic gem cannot be returned to its original state, excavated magic gems need to be handled carefully.
They are also difficult to handle when processing, so only an artisan with excellent skills can be entrusted with it. Additionally, when infusing magical energy into a magic gem, the gem must be of high quality and purity to match the strength of the energy. If the quality of the gem is unsuitable for the greatness of the magical energy, then it won't be able to take it when the energy is poured inside, and it will shatter. For that reason, magic gems of more powerful individuals are regarded as more valuable. Notably, it seems that there still aren't any gems in existence that can contain the magical energy of the Mamono Lord or her husband. Because of the richness of their brilliance, there are passionate collectors of magic gems among both humans and monsters.
Regardless of whether it's the mamono realm or the human realm, magic gems that are infused with the essence or mamono mana of particularly well known people are precious and wildly popular. Such famous people include leader-class monsters of the Mamono Lord's army, or fallen former heroes; as well as current heroes of the Order, and the popes and saints of religious states.
Engagement Rings
Engagement rings are rings that are exchanged at the time of marriage. Originally, monsters had no such tradition, it was a human tradition, but monsters have also come to practice it through the faith of the goddess of love. When a monster couple exchanges engagement rings, these magic gems are often used. The bride and groom will imbue their mamono mana and essence respectively in the magic gems of the two rings and exchange them with each other. The bride will put on the ring of the groom's color, and the groom will put on the ring of the bride's color.
Engagement rings are not necessary for marriage, but even a monster with no interest in jewels will change her tune if it's something that contains the essence of her beloved husband. She'd be very pleased to have proof of the love she shares with her husband, and she'd continue to treasure it. A ring infused with the essence of her husband can make a monster feel like she's always with him whenever she's wearing it.
Furthermore, the color and brilliance of magic gems varies depending on the individual. It would be extremely rare, but it's probably even possible for them to change into mere stones that are poor in color and lack brilliance. However, that sort of thing doesn't matter to monsters. As far as monsters are concerned, what's even more important than the fact that it's a jewel, is the fact that it's a stone containing their husband's essence.[1]
Monster Girl Encyclopedia World Guide - Side II
In Lescatie's diplomacy, a rare mamono realm ore called Druelite, which is mined only here, plays an important role. This red glowing ore has not only a beautiful appearance, but also the ability to amplify stored magical energy. It is used as the main source of energy that solves various problems. Regardless of what mana has been accumulated in it, human or even divine, the output will be enhanced mamono mana, which will have a completely black color. An land where there is a lot of this ore is bound to turn into a mamono realm. As I have been told, Druelite and the goods produced from it are delivered to the poor and barren human lands in various ways.[2]
It was also Castor who discovered the vein of Druelite, which is the most sought after of the products exported by Lescatie. The Druelite mine, now home to the largest vein in Lescatie, turned out to be a cave, something he discovered by chance when he escaped the castle as a boy to explore the world outside. The stone surface of the cave was covered with beautiful crystals that shimmered and flickered. They were what is known as "Gooze ore," which absorbs small amounts of mana from the air and emits a beautiful blue glow. But since the maximum amount of magic these deposits can absorb is small, once a person or monster touches them, the crystals will shatter and only waste rock will remain. In other words, this ore was considered useless because it was not uncommon for crystals to crumble as soon as you pulled them out of the cave. Castor, who had become a diplomat, went to investigate whether he could use the caves he had seen as a child as a tourist spot. In that cave there was still that ore that filled the entire walls, but now it glowed red. "Gooze ore" was transformed by Druella's mana when Lescatie became a mamono realm. The mamono mana absorbed strengthened this mineral and removed its limitations, transforming it into Druelite, which you can safely carry in your hands. Because of the high demand for Druelite, Lescatie now trades with many monster nations. Royal Makai, home of the Mamono Lord's Castle, is one of her big customers.[3]