Bustamite is a calcium manganese inosilicate (chain silicate) and a member of the wollastonite group.

Deer et al.[3] take the formula as (Mn,Ca,Fe)[SiO3] so their value of Z is doubled to 12.

Vesuvianite, wollastonite, garnet, diopside, willemite, johannsenite, margarosanite and clinohedrite also may be present.

At the (new) type locality, Franklin, the oldest rocks are Precambrian gneisses of mixed sedimentary and volcanic origin.

Franklin Marble was deposited within these rocks, along with sediments containing zinc, manganese and iron minerals.