Hematite

Hematite is an iron oxide mineral. Most iron ore deposits consist mainly of hematite, magnetite, or both. Hematite gets its name from the Greek word for blood (haimo) because of the color of its powder and the red streak it leaves when scratched across a piece of unglazed porcelain. Hematite is black, but when powdered or fragmented can show colors ranging from ochre red to jet black. Hematite crystals are a silvery, shiny opaque gemstone that almost looks like metal. Hematite specimens are normally an opaque mineral with a dull luster and it is also known as "black diamond". Historically it was used in the making and coloration of pottery. It was also made into a paste from which beads were made and hardened, and appears commonly today as black beads in costume jewelry. Hematite is an iron ore that is very popular in bead and jewelry designs. Nearly all Hematite beads on the market are manmade materials.

Hematite and magnetite concretions or nodules, sometimes called ironstone concretions, are often mistaken for meteorites because their unusual shapes catch people's attention and they are denser than most other rocks. Hematite concretions are formed in sedimentary rocks by oxidation of pyrite or marcasite (iron sulfide) crystals or precipitation of iron oxide from iron rich solutions. Concretions come in a wide variety of unusual shapes. Sometimes they're shiny on the surface, which might give the impression of a meteorite fusion crust.

While the forms of hematite vary, they all have a rust-red streak. Hematite is harder than pure iron, but much more brittle. Huge deposits of hematite are found in banded iron formations. Grey hematite is typically found in places where there has been standing water or mineral hot springs, such as those in Yellowstone. The mineral can precipitate out of water and collect in layers at the bottom of a lake, spring, or other standing water. But hematite can also occur without water, as the result of volcanic activity.

Hematite appears in many forms in nature, such as Kidney Ore, a bumpy ore that has an appearance likened to a kidney; Hematite Rose, a formation with crystals in the shape of petals; Tiger Iron, a sedimentary rock with Hematite mixed into its multiple layers; Oolitic, sedimentary deposits of small, circular Hematite grains; and Micaceous Hematite, a scaly, shiny stone valued for decorative uses. Its soft Earthy, form is called Red Ochre. Hematite often appears within other crystals such as Aventurine or as phantom crystals.