The rare fossils are not used in the Varrock Museum fossil displays. In OSRS, the museum displays are for small, medium, large, and plant fossils; rare fossils are handled separately.

What to do instead

  • Take rare fossils to the fossil collector on Fossil Island for numulite.
  • If you want Prayer XP, use them for the Strange Machine /related fossil-use content instead of the museum displays.
  • The museum’s fossil section is for building the regular fossil displays to earn XP lamps and kudos.

How the museum fossil section works

  1. Get to Fossil Island first by completing Bone Voyage.
  1. Clean fossils at a cleaning bench after making one, or use the existing setup.
  1. Bring regular fossils to the basement fossil displays in the Varrock Museum and fill the cases with matching fossil types.

Why it seems “locked”

The “rare fossil” area people mention is usually a misunderstanding, because the museum display cases do not accept rare fossils. That’s why you can’t unlock a rare fossil display in Varrock Museum: it isn’t part of the museum system.

Fastest practical answer

If your goal is museum progress, use regular fossils for the Varrock Museum displays. If your goal is to get rid of rare fossils , cash them in elsewhere on Fossil Island.

TL;DR: You don’t unlock a rare fossil section in the Varrock Museum; rare fossils are used outside the museum, while the museum basement displays only accept standard fossil types.