Carnotite, a yellowish mineral found in certain sedimentary rocks, is an important ore of which metal?

Introduction / Context:
Many metallic elements occur in nature not as pure metals but as ores, which are minerals that contain a high enough concentration of the metal to be economically extracted. Recognising the names of important ores is a common requirement in general chemistry and geography. Carnotite is one such ore, noted for its yellow colour and association with radioactive elements. This question asks which metal is obtained from carnotite, so you must connect the ore name with the correct element.

Given Data / Assumptions:
- The mineral in question is carnotite, described in textbooks as a uranium bearing mineral.
- Four metallic elements are listed: uranium, beryllium, chromium, and copper.
- The question focuses on the principal metal of economic interest extracted from carnotite.
- Standard mineralogy data as taught at school and introductory college level is assumed.

Concept / Approach:
Carnotite is a potassium uranium vanadate mineral, often written with a complex formula that includes uranium and vanadium. It occurs in sandstones and other sedimentary rocks and is a significant ore for uranium production. Although vanadium is also present, carnotite is primarily exploited for its uranium content, especially for use in nuclear fuel and related industries. Beryllium, chromium, and copper all have their own characteristic ores, such as beryl for beryllium, chromite for chromium, and chalcopyrite for copper, not carnotite. Therefore the metal associated with carnotite in exam questions is uranium.

Step-by-Step Solution:
Step 1: Recall that carnotite is commonly mentioned in textbooks as a uranium ore, often in the context of radioactive minerals. Step 2: Note that the economic importance of carnotite lies in its uranium content, which can be extracted for nuclear fuel. Step 3: Compare with typical ores of other options. Beryllium is obtained from beryl, chromium from chromite, and copper from ores such as chalcopyrite, malachite, and cuprite. Step 4: Confirm that carnotite is not listed as a main ore for beryllium, chromium, or copper in standard tables. Step 5: Conclude that uranium is the metal for which carnotite is an ore.

Verification / Alternative check:
Mineralogy tables and general science books list carnotite under uranium ores, alongside pitchblende and uraninite. These references describe carnotite as a potassium uranium vanadate with notable radioactivity. They associate it strongly with uranium mining regions and mention vanadium only as a secondary element. No reputable source describes carnotite as a primary ore of beryllium, chromium, or copper. This consistent classification in reference materials verifies that uranium is the correct choice.

Why Other Options Are Wrong:
Beryllium: Generally obtained from minerals like beryl and not from carnotite.
Chromium: Extracted mainly from chromite, a chromium iron oxide mineral, not from carnotite.
Copper: Mined from ores such as chalcopyrite, malachite, and cuprite, not from carnotite which is associated with uranium and vanadium.

Common Pitfalls:
A common error is to confuse different ore names because many sound somewhat similar or are associated with mining regions in general. Another mistake is to assume that any ore with a complex formula might be related to a widely used metal like copper without checking specific textbook tables. To avoid such problems, it is helpful to memorise short lists of important ores: for example, bauxite for aluminium, hematite and magnetite for iron, and carnotite and pitchblende for uranium. This creates strong mental associations that make exam questions easier to answer.

Final Answer:
Carnotite is an important ore of Uranium, which is extracted from this mineral for use in nuclear energy and related applications.