Step 1: Understanding minerals of sulfur.
Cinnabar is the primary ore of sulfur, containing mercury sulfide (HgS). Other listed minerals do not contain sulfur as their main component.
Step 2: Analyzing the options.
(A) Fluorapatite: This is a phosphate mineral and does not contain sulfur.
(B) Carnalite: This is a mineral of potassium and magnesium chloride, not sulfur.
(C) Cinnabar: Correct — Cinnabar is a mineral of sulfur.
(D) Sylvine: This is a potassium chloride mineral and does not contain sulfur.
Step 3: Conclusion.
The correct answer is (C) Cinnabar.