Local quarrymen refer to the easily worked Globigerina Limestone as franka; the harder-wearing coralline limestones are called zonqor. Both were widely used in the building of the islands’ massive fortifications.

FIRST QUALITY LIMESTONE (local name Gebel tal Qammi or Zonqor tal-Prima)
It is a hard, non-porous, recrystallized and polishable limestone or marble.
Varies in colour from white, yellow and brownish to reddish and greenish.

SECOND QUALITY LIMESTONE (local name Zonqor tas-Seconda)
It is a hard, porous, recrystallized and polishable limestone or marble. It also
varies in colour as does the first quality limestone. However, it is softer and
less resistant to weather.

Both qualities have been used for floors, pavements, steps and foundations,
and laid in blocks; today they are used only as raw material for manufacturing
aggregates.