Question

Which one of the following textures is called the chalcopyrite disease?

• A. Chalcopyrite blebs in sphalerite
• B. Sphalerite stars in chalcopyrite
• C. Chalcopyrite lamellae in bornite
• D. Bornite lamellae in chalcopyrite

Hint:

In ore microscopy, always remember: chalcopyrite disease refers to chalcopyrite blebs in sphalerite, while exsolution lamellae (chalcopyrite–bornite) are different textural phenomena.

Answer 1

The Correct Option is A

Step 1: Understanding the term “Chalcopyrite disease.”
The phrase \textit{chalcopyrite disease} refers to the microscopic occurrence of tiny blebs, rods, or dust-like inclusions of chalcopyrite dispersed within sphalerite. This term is commonly used in ore microscopy. Step 2: How does it form?
- Sphalerite (ZnS) often contains trace amounts of iron.
- During cooling or later alteration, the excess Fe exsolves with Cu to form extremely fine inclusions of chalcopyrite within sphalerite.
- This gives a spotted or “diseased” appearance under the microscope, hence the name “chalcopyrite disease.” Step 3: Elimination of other options.
- (B) Sphalerite stars in chalcopyrite $\Rightarrow$ Not a recognized texture.
- (C) Chalcopyrite lamellae in bornite $\Rightarrow$ This is a separate exsolution texture, not chalcopyrite disease.
- (D) Bornite lamellae in chalcopyrite $\Rightarrow$ Also unrelated to the term.
Step 4: Conclusion.
Therefore, the texture specifically called “chalcopyrite disease” is chalcopyrite blebs in sphalerite. \[ \boxed{\text{Chalcopyrite blebs in sphalerite = Chalcopyrite disease.}} \]