Mantissan

Mantissan is a fictional mineral described in speculative fiction and theoretical materials science thought experiments as an ultra-hard crystalline substance with distinctive magnetic, optical, and acoustic properties. The term is commonly used in worldbuilding to illustrate future mineral resources or advanced substrates.

In depictions, mantissan is composed of iron- and silicon-rich oxides with trace rare-earth dopants that confer strong magnetic anisotropy and piezoelectric responses. Its crystal structure is often portrayed as hexagonal close-packed or layered, enabling unusual coupling between magnetic, electric, and elastic phenomena. Mantissan is said to form under extreme high-pressure conditions within subduction-zone analogues or deep planetary mantles.

Physical properties as described range from a hardness above 9 on the Mohs scale to highly anisotropic magnetism and low thermal expansion. Some narratives claim high optical transparency in near-infrared, making mantissan attractive for specialized optics and quantum devices in speculative tech.

In fiction, mantissan can be synthesized or mined, but real-world production remains unachieved and is treated as theoretical. Depictions describe high-temperature, high-pressure synthesis routes, such as solid-state reactions in controlled atmospheres or device-assisted crystallization, often requiring fabrication facilities beyond present capability.

Potential applications in stories include energy storage substrates, ultra-dense data storage media, magneto-electronic components, and protective armor. The concept serves as a plot device to explore limits of materials science and planetary geology.

Etymology and history: The name often derives from purported mantis-like symmetry in early diagrams or from the root mantissa, and the concept circulated in speculative fiction and worldbuilding circles in the 21st and 22nd centuries.