What’s your favorite mineral? Mine is a spunky, isometric mineral called Franklinite. Franklinite is in the spinel group with many other minerals that have a cubic or isometric crystal system. The spinel group, specifically the iron spinel group consists of minerals such as magnetite, which is commonly used in steel production, and zinc ferrite, that is used as a pigment. Like the name of the subgroup, all minerals in the iron spinel group contains the element Fe or Iron. But unlike the other minerals, Franklinite caught my attention the most.
Franklinite was discovered in 1819 in Franklin, New Jersey and was named after the place it was found and America’s Inventor, Benjamin Franklin. Mentioned before, Franklinite is a mineral in the iron spinel group and has an isometric crystal system. The mineral itself is a metamorphic rock and has the hardness of 5.5 to 6. Although the chemical formula for pure Franklinite is (Zn,Fe2+)(Fe3+)2O4, Franklinite is usually found with manganese making the more recognizable formula: (Zn,Mn2+,Fe2+)(Fe3+,Mn3+)2O4.
Here’s a fun fact: Franklinite used to be an important ore of zinc during the time the Franklin and Sterling Hill mines were open. The mines eventually closed down, the use of Franklinite in zinc died and it became no longer an important ore in zinc production. However, the mineral is still an important ore of iron making it the reason for its name in the subgroup.
Color catches the people’s attention the most. Franklinite’s color mainly ranges from black to grey with frequent occurrences of white. Although in some photos it’s hard to notice, Franklinite has streaks that are reddish brown to black and fragments that are known to be translucent. There are also times where different minerals would be intertwined with Franklinite. But in most cases, the mineral would be zinc which looks red and splotchy.
You may wonder why a dull-colored mineral like Franklinite caught my attention, but personally I find dark and metallic colors the most appealing to my eyes. Not only was it the color, but it was also the octahedral form of the mineral itself. I found the shape of the mineral and the fact that it becomes fluorescent under UV light mesmerizing. Almost like granite or marble, the dark colors of the mineral show the strata of the rock and the patterns and lines that appear from the layers to make interesting indents and outlines. There are also times where the mineral looks like graphite and as if you can draw or write with it. All these facts make something that may seem dull from first sight interesting and aesthetically beautiful.