Which of the following minerals is an ore of iron that is used in the metallurgical industry?

Introduction / Context:
Ores are naturally occurring minerals from which metals can be extracted economically. Knowing which minerals are important ores for major metals such as iron, copper, and lead is a common requirement in general science and geography. This question asks you to identify which of the listed minerals is an ore of iron, linking mineral names to their associated metals.

Given Data / Assumptions:

• The options are dolomite, Epsom salt, siderite, and galena.
• The question is specifically about an ore of iron, not other metals.
• We assume standard mineral definitions: chemical formulas and associated metals.

Concept / Approach:
Siderite is an iron carbonate mineral with the formula FeCO3 and is recognised as an ore of iron. Dolomite is a calcium magnesium carbonate (CaMg(CO3)2) and is used as a source of magnesium and as a building stone, not primarily as an iron ore. Epsom salt is hydrated magnesium sulphate (MgSO4·7H2O), used in medicine and agriculture. Galena is lead sulphide (PbS) and is the chief ore of lead. Therefore, among the options, only siderite is an iron ore.

Step-by-Step Solution:
1. Identify siderite as an iron carbonate with the chemical formula FeCO3, indicating the presence of iron.2. Recognise that siderite can be processed to extract iron metal and is thus classified as an iron ore.3. Dolomite, CaMg(CO3)2, contains calcium and magnesium, not iron, and is used more as a building stone and source of magnesium.4. Epsom salt, MgSO4·7H2O, is a magnesium salt used in bath salts and agriculture, not an iron ore.5. Galena, PbS, is the most important ore of lead, not iron.6. Therefore, the only mineral listed that serves as an ore of iron is siderite.

Verification / Alternative check:
Lists of iron ores in textbooks and encyclopedias typically include hematite (Fe2O3), magnetite (Fe3O4), limonite (hydrated iron oxides), and siderite (FeCO3). Each of these contains a high proportion of iron and can be used in smelting. Dolomite and Epsom salt appear in discussions of magnesium compounds. Galena appears in sections on lead ores. The grouping of these minerals by metal in standard references confirms that siderite is the iron ore among the options.

Why Other Options Are Wrong:
Option A, dolomite, is not an iron ore; it is associated with calcium and magnesium and is used in construction and agriculture. Option B, Epsom salt, is magnesium sulphate and has no iron content. Option D, galena, is the chief ore of lead, not iron. None of these can be classified as an iron ore in the usual sense.

Common Pitfalls:
Students sometimes choose galena because it is a familiar ore name, forgetting that it is linked to lead. Another pitfall is to select dolomite or Epsom salt by guessing, without remembering their composition. To avoid mistakes, it is helpful to associate a few key ores with their metals: siderite and hematite with iron, galena with lead, and bauxite with aluminium, for example.

Final Answer:
The ore of iron among the given minerals is siderite.