Zebetite



Zebetite, also referred to as Zeebetite, is a powerful ore located in Tourian. It seems to be a powerful source of energy that powers the Mother Brain. The only times Samus has needed to destroy Zebetites is to get to Mother Brain in all of her encounters; although they can be destroyed with Missiles, Zebetites regenerate in a matter of seconds if Samus does not dispatch them quickly (also wasting precious ammuniton), making them excellent shields for protecting the Pirate leader. It is possible Zebetites are somewhat living tissue. They are featured in Metroid, Super Metroid, and Metroid: Zero Mission. Also, objects resembling Zebetites which also diminish in thickness when fired at appear in some Space Pirate facilities in Metroid Prime 3: Corruption. However these variants do not regenerate, and will respawn once Samus leaves the rooms in which they are found, unlike the Zebetites encountered in the 2D games. The environment artist who designed them, Matt Manchester, made them with the Zebetite in mind.

In the manga, Mother Brain states that her Zebetite shields can deflect particles, rendering Samus' power beam useless. 

Metroid manual
"This energy source is vital for keeping Mother Brain alive. It is no more than a life-supporting system and therefore won't attack, but it must be destroyed and only missiles will do the job. One missile blast is not enough. Other weapons are harmless against it. You have to keep throwing missiles or it will simply come to life again."

1986 manga
"Mother Brain's life support system. Nothing but Missiles can destroy them."

Official Nintendo Player's Guide
"This is Mother Brain’s energy source. It can be destroyed with continuous missile attacks."

Matt Manchester's notes
"These hallways were designed to have destructible barrels throughout that you could shoot to damage enemies with. I wanted to tie in Space Pirate tech from earlier games, so I made them a variation of the "zebetites" from the first metroid, which were the collapsing canisters you had to shoot through to get to Mother Brain at the end of the game."

Captain N: The Game Master
Zebetite is referred to as Mother Brain's energy source for herself and Metroid in the Captain N: The Game Master show and comics. In the episode Metroid, Sweet Metroid she managed to trick the team into thinking "Power Flowers" (really ordinary flowers) fueled her and the asteroid called Metroid, and when they cut off the supply of flowers that she was shut down for good so Kevin could warp back home (which ended up leading to a fake replica of his town). When he was captured, she sad she had "enough Zebetite powered crystals to power Videoland ten times over." After that incident, the characters have tried to sabatoge shipments of the Zebetite a few occasions during the TV series and comics (Money Changes Everything). Shots from Kevin's Zapper are said to bounce off (similar to the later manga interpretation of it), while Samus states that only her missiles can affect it.

Trivia

 * The theme of Mother Brain in Metroid and Zero Mission is called "Zebetite" on the Super Metroid: Sound in Action CD.