The sheets can be thought of as being like chicken wire with alternating octagon and square shaped holes. Only carletonite and other members of the Apophyllite Group have this unique interconnected four and eight-member ring structure. Color is blue, white, colorless or pink. Color zoning is common. Luster is vitreous to dull.
Crystals are translucent to less commonly transparent.
Crystal Habits include prisms truncated with a pinacoid termination. The prisms are predominantly four sided but may display small secondary faces giving a slight octagonal cross-section. Phantoms are seen in some transparent crystals. Fracture is conchoidal. Hardness is 4.5 - 5.