Iron Ores – Maximum Iron Content by Mineral Type Considering common iron ores used in metallurgy, which ore contains iron up to about 72% by mass, making it one of the richest natural sources?

Introduction:
Ore evaluation often starts with theoretical iron percentage from mineral formulae. The question asks you to identify the ore with the highest iron content among common natural minerals used in ironmaking.

Given Data / Assumptions:

• Candidate minerals: magnetite, haematite, limonite, siderite, and pyrite.
• We compare theoretical iron percentages implied by chemical formulae.
• Processing complications (e.g., sulphur in pyrites) are secondary to Fe% in this question.

Concept / Approach:

Calculate/recall theoretical Fe%: magnetite ≈ 72.4%, haematite ≈ 69.9%, siderite ≈ 48.2%, limonite variable and lower due to combined water, pyrite unsuitable with only ≈ 46.6% Fe and high sulphur.

Step-by-Step Solution:

Verification / Alternative check:

Standard mineralogy tables list magnetite at about 72.4% Fe, the highest among the options provided.

Why Other Options Are Wrong:

Haematite: slightly lower Fe%. Limonite: hydrated, lower Fe%. Siderite: carbonate with lower Fe%. Pyrites: sulphide with problematic sulphur and lower Fe%.

Common Pitfalls:

Picking haematite due to its widespread use without checking theoretical Fe%; ignoring hydration/carbonate/sulphide penalties.

Final Answer:

Magnetite (Fe3O4)