Conversation so far:
What was the Spirit's main discovery?
Analysis shows that the rocks have been slightly altered by tiny amounts of water.
Which Martian rocks were analysed?
All the rocks contain a fine coating of dust and one or more harder rinds of material.
What materials do Martian rocks contain?
They contain the minerals olivine, pyroxene, plagioclase, and magnetite, and they look like volcanic basalt as they are fine-grained with irregular holes.

Question: Where were these rocks found?
Self-contained rewrite: Where were Martian rocks found?