the black stone is just there for hajj performers to remember how many times they've been round the Ka'ba [that cube shaped mosque], once they come round once, they indicate towards it, or if their near enough, they kiss it and thus note that they've been round once, twice, etc,; one hadith say it all about the significance of the black stone:
Sahih Al Bukhari, Volume 2, Book of Hajj, Chapter 57, Hadith 1605. Umar (ra) said, “I know that you are a stone and can neither benefit nor harm. Had I not seen the Prophet (pbuh) touching (and kissing) you, I would never have touched (and kissed) you”.
Sahih Al Bukhari, Volume 2, Book of Hajj, Chapter 57, Hadith 1605. Umar (ra) said, “I know that you are a stone and can neither benefit nor harm. Had I not seen the Prophet (pbuh) touching (and kissing) you, I would never have touched (and kissed) you”.