A few elements like carbon, sulphur, gold and noble gases, occur in free state while others are found in combined forms in the earth’s crust. Elements vary in abundance. Among metals, aluminium is the most abundant. In fact, it is the third most abundant element in earth’s crust (8.3% approx. by weight). It is a major component of many igneous minerals including mica and clays. Many gemstones are impure forms of Al₂O₃. For example, gems ‘ruby’ and ‘sapphire’ have Cr and Co respectively as impurity. Iron is the second most abundant metal in the earth’s crust. It forms a variety of compounds and their various uses make it a very important element. It is one of the essential elements in biological systems as well.

For obtaining a particular metal, first we look for minerals which are naturally occurring chemical substances in the earth’s crust and are obtained through mining. Out of many minerals in which a metal may be found, only a few are viable to be used as source of that metal. Such minerals are known as ores.

What is the formula of Siderite?

FeCO₃

The correct answer is option 1. \(FeCO_3\).

Siderite is a mineral composed primarily of iron(II) carbonate, with the chemical formula FeCO3. Here's a detailed explanation:

Composition:

Siderite is a carbonate mineral, meaning it contains carbonate ions \((CO_3^{2-})\) as a fundamental component. The iron in siderite is in the \(+2\) oxidation state, hence the name iron(II) carbonate. The iron ions \((Fe^{2+})\) are bonded to carbonate ions in the mineral structure.

Physical Properties:

Siderite typically occurs in earthy to crystalline forms and may exhibit colors ranging from yellowish-brown to dark brown. It has a Mohs hardness of around 3.5 to 4.5, making it relatively soft compared to many other minerals. Siderite often forms rhombohedral or scalenohedral crystals, but it can also occur as massive aggregates or concretions.

Occurrence:

Siderite is commonly found in sedimentary environments, especially in association with iron-rich sedimentary rocks such as banded iron formations. It occurs as a primary mineral in sedimentary iron ore deposits and can also form as a secondary mineral through chemical alteration of other iron-bearing minerals.

Uses:

Siderite is an important iron ore mineral and serves as a significant source of iron. Historically, siderite has been mined and used for iron smelting, although it is less commonly exploited compared to other iron ores such as hematite and magnetite. In addition to its industrial importance, siderite also has some minor uses in the production of pigments and as a gemstone in jewelry.

Overall, siderite is a notable iron-bearing mineral with the chemical formula FeCO3. It is valued for its iron content and occurs in various geological settings, primarily in sedimentary environments.