[2] It often contains lead, which was detrimental to the zinc smelting process, so it was not a useful ore mineral.

[5] Like many of the famous Franklin minerals, hardystonite responds to short wave ultraviolet (254 nm wavelength) light, emitting a fluorescence from dark purple to bright violet blue.

In daylight, it is white to gray to light pink in color, sometimes with a vitreous or greasy luster.

It is very rarely found as well formed crystals, and these are usually rectangular in appearance and rock-locked.

[6] Other minerals often associated with hardystonite are franklinite, diopside, andradite garnet, and esperite (fluoresces yellow).