The first episode of "Game of Thrones" Season 8 premiered April 14. It has been two years since the last time HBO released an episode of the TV series adaptation of George RR Martin’s bestselling epic medieval fantasy book “A Song of Ice and Fire.”

Since “Winter is Here” and the White Walkers are coming south of The Wall, Northerners are preparing for the battle of the living and the undead. In "Game of Thrones" ("GoT"), one of the many ways to harm or kill White Walkers is with the use of dragonglass. "GoT" fans are aware that Samwell Tarly discovered dragonglass by chance back in Season 2.

Through Samwell Tarly’s research on White Walkers at the Citadel in Oldtown in Season 7, it was revealed that an enormous supply of dragonglass is found in Dragonstone, an island located near Blackwater Bay which has been the ancestral home of the House Targaryen before the Conquest.

To assist us in understanding what dragonglass truly is in real life, the Natural History Museum of London has been sharing photos of their curated dragonglass or obsidian.

“In the absence of fire-breathing reptiles, obsidian is formed by rapidly cooling lava,” a Twitter post from London’s Natural History Museum read. “The volcanic glass lacks a crystal structure, so is hard and brittle, and fractures with sharp edges.”

Obsidian is a black, naturally-occurring igneous rock formed by the rapid cooling of viscous lava from volcanic eruptions. It is a rock that is extremely hard and brittle, which means it can be used to form blades, arrowheads and spears. Unlike dragonglass, it cannot be forged like metal. Obsidian can only be shaped by chipping away portions of the stone the same way hand axe was created by the Neanderthals thousands of years ago.

Dragonglass is similar to obsidian in the real world in that it is used as a tool or weapon. But obviously, obsidian is not created because of the dragon fire.

Game of Thrones Jaime’s (Nikolaj Coster-Waldau) arrival in Winterfell brings new tensions on Season 8, Episode 2 of “Game of Thrones.” Photo: Helen Sloan/HBO