I would like to know what type of rock is the big one in the upper part. It has a density between 3.75 and 4.5, a white streak and when it's hit, it smells slightly like rotten eggs, so I guess it contains sulfur. It was found in Zaragoza, Aragon; located in the northern part of Spain. Thanks in advance!
Not necessarily....lots of rocks, especially quartz-rich rocks, give off a noticeable "gunpowder" smell when violently fractured. I'm not sure where it comes from but I've noticed it when manually smashing large cobbles, and in mountain gullies after rockfall.
Your rock could well be a quartzite cobble.