Pure silver (or "fine silver) is very soft and therefore not very durable; it's amalgamated with other metals (as noted, usually copper) to make it stronger. Pure silver does NOT tarnish; copper does.

What type of silver does not turn black?

Discovered the right mineral right after I posted this. Did you know though there seems to be a new process of melting the silver so it won't tarnish. This silver is called Argentium silver.

Which silver does not tarnish?

Sterling silver, even real . 925 sterling silver, will always tarnish. While pure 99.9% silver does not tarnish, any sterling silver will tarnish over time as a result of the metal mixed in.