Magnesite
Magnesite was a form of magnesium carbonate (MgCO3). This mineral could interfere  with sensor and transporter functions. (; ) 

In the mid-22nd century, Starfleet used magnesite in the production of their warp reactors. ()

In 2151, Malcolm Reed and Travis Mayweather broke a drilling rig's bit when the drill hit a layer of magnesite on Archer's Comet. ()

In 2154, Harrad-Sar, an Orion trader, offered Captain Archer the coordinates of a planet rich in magnesite as part of a deal between Starfleet and the Orion Syndicate. ()

In the 24th century, magnesite fuel had replaced wood as the standard material for fires in the Federation. ()

In 2370, the Duras sisters and their associate Gorta illegally mined over ten thousand kilograms of magnesite from the Pakled-owned planet of Kalla III. The  tracked the magnesite to a Yridian buyer while the transaction was still taking place. Commander Riker purchased the Yridians' magnesite, and then beamed it into space and fired phasers on it to expose the Duras sisters' cloaked Bird-of-Prey. ()

In 2371, an away team from  was investigating magnesite deposits on a planet near the Avery system when they were captured by Vidiians. ()

Magnesite was used in the hulls of Kazon fighters. ()

A Federation hospital on Ajilon Prime was located near a large deposit of magnesite, preventing Julian Bashir and Jake Sisko from transporting to the surface in 2373. ()

The surface of the planet Arakis Prime had a layer of magnesite dust. ()

Magnesite could provide partial protection against antimatter radiation. After an antimatter accident, 's people in the Delta Quadrant hid in magnesite-rich caves and lined makeshift environmental suits with magnesite to survive the radiation. However, they still suffered from widespread radiation poisoning. ()

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