Your fifth is black, and can be found buried in fiberglass
You are the
Periodic table of elements
The clues each have a property of a member, along with a couple words containing the "name":
Hydrogen:
sunny (it's found in the sun)
H is in here and Hades
Helium:
funny (you talk funny when inhaled)
He in here and Hell
Lithium:
charged (commonly used in batteries)
Li in liberated and Alicante
Beryllium:
rare (it's just rare, and not found alone)
Be in liberated and Iberia
Carbon:
hard (think diamonds)
C in secretly and knickers
Nitrogen:
fertile (most fertilizers contain it)
N in often and pants
So that makes the fifth one:
Boron:
black (one of it's "natural" appearances)
B in buried and fiberglass
Thanks to GentlePurpleRain in comments for the last set of clues.