Bog iron

Classification：Sedimentary Rock

A type of iron ore consisting of limonite and clay or plant debris. A porous rock formed in swamps, wetlands and shallow lakes. Tietong is precipitated from water through the oxidation of bacteria and algae. The common Scandinavian and North American cold temperate regions.

Bog iron is also called goethite. It is a widely distributed iron oxide. The rust commonly seen is basically composed of it.

Brief introduction:
Bog iron is also called goethite. It is a widely distributed iron oxide. The rust that we usually see is basically composed of it. Generally speaking, goethite is formed by other iron ores (such as pyrite, magnetite, etc.) under weathering conditions.

Bog iron can also be formed on the bottom of the sea or lake by deposition. Goethite is a relatively important iron ore. Besides iron extraction, it is also used as yellow ocher pigment. The color of goethite is from yellow brown to red, and the crystals are flaky, columnar or needle like. The aggregate of crystals is generally spherical, clocked or massive with concentric and radial fibers.

History：
Goethite is a widely distributed mineral. As a kind of hydrated iron oxide, the importance of goethite in the existing iron ore is second only to hematite (hematite, alpha). Its western name comes from the famous German poet Gerd (J.W. von Goethe, 1749-1832). The name of the scholar who was keen to collect minerals in the field was recorded as a common mineral in 1806. At first, this name was used to describe another mineral now known as [lepidocrocite, -FeO (OH)). The latter is homogenous and homogeneous with goethite (that is, the common chemical composition but the crystal structure is different): the arrangement of oxygen and hydroxyl ions in goethite presents the most dense six square accumulation, while the fibrite is cubic accumulation, two The iron ions are distributed in a eight body gap.

Cause:
In the cause of origin, the weathering products of iron containing minerals under oxidation conditions are the most common, for example, the main composition of the so-called limonite is Bog iron. For the same reason, some of the outer and outcrop weathering iron caps of copper and iron ore bodies (such as the pyrite in Arizona, America), and the accumulation of some red soil formed by the weathering of the serpentine (such as some red earth iron ore in Cuba), are also made up of goethite as the main body. Deposition is also another common form, which can be directly precipitated and possibly biogenic. This kind of goethite is often found around the bottom sediments and springs of the lake, and these layered or nodular amorphous goethite is sometimes called the Bog iron (Bog Iron Ore). Finally, there is a relatively rare form. People will also find the mineral formed by low temperature hydrothermal in some hydrothermal veins. In addition, it is necessary to explain that, under regional metamorphism, this kind of mineral (including other hydrous iron oxide minerals) dehydrated to form hematite or magnetite.

Appraisal：
As for identification, as a crystal mineral with fixed components, it is easy to distinguish if crystalline is intact. But more often, the mineral will appear in amorphous form. At that time, we can't rely solely on observation. Because of this, the concept of iron iron, a kind of iron ore that humans have been using early, has not come out of the "limonite", a less scientific name, until 1806. People begin to realize that limonite, the impure, amorphous substance in most mining areas, can be identified as actually a goethite (specifically, the mineral mainly), and until the birth of the X ray diffraction method, "limonite" as a point of view of an independent mineral comes out of the people's field of vision.

Application:
In application, it was first used as a pigment called the "ochre" pigment; of course, as the main primary mineral of the limonite in many areas, the iron material is naturally an important application form, for example, in its largest producing area, the Alsace Lorraine basin, France. In addition to the areas mentioned above, iron ore in the Great Lakes region of North America and the alaachian mountains south of Shannan, Labrador Peninsula and parts of South Africa, Brazil and Australia is also an important source of mineral production. Finally, it should be noted that if the mineral continues to hydrate, the subspecies produced is called water goethite.
Note: the limonite is actually an amorphous mineral formed by hydration of goethite and fibronite. Because it is usually not pure, or it will contain the two primary minerals, it is not considered as an independent mineral. In most of the limonite ore, the primary minerals are goethite.

Chemical composition:
Alpha -FeO (OH)

Optical properties:
Two axis crystal (-). Np=2.260, Nm=2.393, Ng=2.398 (Na). 2V is small to medium. Polychromatic is weaker than fibrous iron ore, Np- yellow, Nm- brown yellow, Ng- orange. Strong dispersion, r>v. Np//b, Bm//c, Ng//a. The reflected color gray is blue and is darker than the fibrinolytic iron ore. Reflectivity: 17.5 (Lv Guang), 14 (Cheng Guang), 13 (Hong Guang). The double reflexes are weak.
Goethite is a widely distributed oxide of iron. Goethite from exogenous origin is the main component of limonite. Goethite mainly forms an exogenous process, which is produced by the oxidation and decomposition of iron containing minerals, such as pyrite, siderite, magnetite and iron silicate, which are formed by oxidation and decomposition. It is often associated with hematite, manganese oxides, calcite, clay and so on.