Sussexite is a borate mineral MnBO2(OH).

It is named after the Franklin Mining District in Sussex County, New Jersey,USA where it was first discovered.

Colour is white, pink, yellowish white. Hardness 3.

Sussexite also occurs in France, Italy, Namibia, North Korea, South Africa, Switzerland, and the US states of Michigan, New Jersey, Utah, and Virginia. Crystals are orthorhombic. Forms fibrous veins and masses.