Franklinite

Franklinite or Zinkoferrit is a rarely occurring mineral from the mineral class of oxides and hydroxides. It crystallizes in the cubic crystal system with the chemical composition (Zn, Mn2 , Fe2 ) ( Fe3 , Mn3 ) 2O4 in the spinel - type and forms up to 22 cm large octahedral crystals, often with rounded corners. Also, coarse or fine-grained inclusions in other minerals are found. Franklinite is grayish black to black in color and has inner dark red reflections.

Etymology and history

The mineral was first found in 1819 by Pierre Berthier in the type localities, several mines around the town of Franklin in the State of New Jersey. It is also named after this.

Classification

In the classification by Strunz Franklinite is counted among the oxides with a ratio of metal to oxygen of 3:4. After the 8th edition forms a group together with Cuprospinell, Jakobsit, Magnesioferrit, magnetite and Trevorit. In the 9th edition it forms with Brunogeierit, chromite, Cochromit, Coulsonit, Cuprospinell, Filipstadit, gahnite, galaxite, hercynite, Jakobsit, Magnesiochromite, Magnesiocoulsonit, Magnesioferrit, magnetite, Manganochromit, Nichromit, Qandilit, spinel, Tegengrenit, Trevorit, Ulvöspinell, Vuorelainenit Zinkochromit and a sub- group of the oxides, with a ratio of metal to oxygen of 3:4 and medium cations.

In the classification by Dana it forms with Magnesioferrit, Jakobsit, magnetite, Trevorit, Cuprospinell and Brunogeierit the iron subgroup of the spinel group, one of the multiple oxides.

Education and Locations

Franklinite forms in veins through metamorphosis at high temperatures from marine carbonate sediments, which are iron -, zinc-and manganese- rich. It is associated with zincite, willemite, calcite, andradite, Manganosit, Rhodochrosite, gahnite, magnetite, rhodonite, hausmannite, Hetaerolit, Jakobsit, Braunite, Sarkinit, Berzeliit and hematite.

In addition to the type locality in Franklin are finds from the Eyre Peninsula and Mukinbudin in Australia, Letmathe in Germany, Ross Iceland in Ireland, Kazakhstan, Santa Eulalia in Mexico, Nežilovo in Macedonia, Slyudiyanka, Buryatia and Chibinen in Russia, Barberton in South Africa, Garpenberg, Filipstad and Hällefors in Sweden and the U.S. states of Alaska, California, Colorado, Nevada, New Jersey and New Mexico known.

Crystal structure

Maldonit crystallizes in the cubic crystal system in the space group with the lattice parameters a = 8.45 Å, and eight formula units per unit cell.