The stone can look silver-gray, black, brown or red, shine in the form of metallic crystals or be as dull as a reddish rough ...

Then, in March, Spirit hit a jackpot: a volcanic rock whose composition hinted at a watery past. Three months later, NASA was surprised when Spirit stumbled across hematite, adding evidence to the ...

An obstacle for testing this idea, however, has been the lack of an age for the rocks to reveal when the ... We found veins of hematite and quartz that both cut through Tava dikes and were ...