Conservationist

Conservationists are a sapient species of metallic-based life forms which evolved on a planet without free oxygen. Their bodies are stone-like, with a crystalline nervous system, and their metabolism is based on reducing metal oxides or sulfides to free metal. While most individuals are sessile, some acquire mobility by encasing themselves in machinery connected directly to their nervous system. Such individuals can travel through space and appear like living spacecraft.

Conservationists don't recognize organic life forms as being truly alive and seem oblivious to the possibility of any organic creature being sapient.

They are so named because their civilization is so large that the conservation of resources is pivotal for their short-term survival.

Biology
Conservationists are an extraordinarily long-lived species with stone-like flesh embedded with metallic calcium-based crystals forming their nervous system. They live for several million years, move extremely slowly and communicate by radio waves. Their sensory organs are also based on radio. They can tolerate free oxygen for a few hours before it starts causing damage to their skin and tissues.

While they can take millennia to move physically from one location to another, their thought processes are paradoxically much faster, to the point that they can think and conjure hypotheses in milliseconds. This is because their metallic neurons transmit messages by electronic currents and work much faster than organic organisms which use neurochemical impulses.

Although they have no eyes, the crystals that make up their nervous system are naturally photosensitive, and they are able to attach artificial lenses directly to their skin and learn how to interpret the images.

Culture and society
Their civilization is billions of years old and spans across the Milky Way Galaxy, concentrated in the galactic core. They are highly dependent on their organized galaxy-wide network for identifying metal resources, mining them and distributing them. Even a small scale miscalculation in this vast operation can easily result in several worlds being condemned to starvation.

Most individuals are sessile and regard themselves as a sort of intellectual elite. Those comparative few who are encased in machinery that allows them to perform work are seen as unsophisticated by the others, even though their pivotal social role is acknowledged.

Appearances

 * "Planetfall", by Hal Clement (1957)