Jacium in its pure form is a brittle, light grey substance that can be found on some worlds. It has the ability to merge into the molecular structure of a number of other metallic or crystalline substances where it enhances their structural integrity. Jacium enhanced compounds are much harder than the original materials but tend to chip and break under stress rather than to bend. This makes them useful for the construction of strong lightweight support structures but woefully unsuitable for uses associated with shock absorption, i.e. armour.