Calcium (Ca #20) is the next element on the periodic table for my APEX mineral collection.Wikipedia Calcium
Calcium Minerals - There are many Calcium minerals.Fluorite (CaF2) with 51% Calcium is my choice for APEX Mineral. Other minerals with more Calcium are not common and are highly reactive.
Lime as building material was used since prehistoric times going as far back as 7000 to 14000 BC
Calcium minerals are mainly used in cements and mortars.