[4] It occurs in association with apophyllite, natrolite, thaumasite, merwinite, spurrite, gehlenite, ettringite, portlandite, hillebrandite, foshagite, brucite and calcite.

[4] It was first described in 1925 for an occurrence in the Dutoitspan Mine, Kimberley, South Africa and was named for Alpheus Fuller Williams (1874–1953), a past official of the De Beers diamond company.

Jennite, afwillite, oyelite and calcite are all minerals that form in layers within spurrite veins.

[6] Contact metamorphism is caused by the interaction of rock with heat and/or fluids from a nearby crystallizing silicate magma.

When viewed under crossed polarizers in a petrographic microscope, it displays first-order orange colors, giving a maximum birefringence of 0.0167 (determined by using the Michel–Levy chart).

Afwillite is composed of double chains that consist of calcium and silicon polyhedral connected to each other by sharing corners and edges.