a group of 4 different hematite specimens offered at a reduced price
|Specimen||weight (g)||dimension (cm)|
|botryoidal hematite with quartz Florence Mine, Cumbria||112||6x4x2.4|
|botryoidal hematite Morocco||80||5.5x4x2|
|specular hematite with quartz Florence Mine, Cumbria||24||4x3x1.5|
This is an important ore of iron and is blood red colour in the powdered form. It is often used as a colourant. It gets its name from the Greek hema for blood, as in haemaglobin, because of the colour of its powder.
Crystals of Hematite are considered rare and are sought after by collectors, as are fine Kidney Ore specimens. Hematite was so named because of the fact that when cut, the saw coolant becomes blood red.
Hematite is found as a primary mineral and as an alteration product in igneous, metamorphic, and sedimentary rocks. It can crystallize during the differentiation of a magma or precipitate from hydrothermal fluids moving through a rock mass. It can also form during contact metamorphism when hot magmas react with adjacent rocks.
The most important hematite deposits formed in sedimentary environments. About 2.4 billion years ago, Earth’s oceans were rich in dissolved iron, but very little free oxygen was present in the water. Then a group of cyanobacteria became capable of photosynthesis. The bacteria used sunlight as an energy source to convert carbon dioxide and water into carbohydrates, oxygen, and water. This reaction released the first free oxygen into the ocean environment. The new oxygen immediately combined with the iron to form hematite, which sank to the bottom of the seafloor and became the rock units that we know today as the banded iron formations.
Soon, photosynthesis was occurring in many parts of Earth’s oceans, and extensive hematite deposits were accumulating on the seafloor. This deposition continued for hundreds of millions of years – from about 2.4 to 1.8 million years ago. This allowed the formation of iron deposits hundreds to several thousand feet thick that are laterally persistent over hundreds to thousands of square miles. They comprise some of the largest rock formations in Earth’s rock record.
Many of the sedimentary iron deposits contain both hematite and magnetite as well as other iron minerals. These are often in intimate association, and the ore is mined, crushed, and processed to recover both minerals. Historically, much of the hematite was not recovered and was sent to tailings piles. More efficient processing today allows more hematite to be recovered from the ore. The tailings can also be reprocessed to recover additional iron and reduce tailings volume.