Name a sulphide ore which is not concentrated by froth floatation process. Why is it so ?

Explanation

### Step-by-Step Solution:

1. **Identify Sulphide Ores**: Sulphide ores are minerals that contain metal sulfides. Common examples include galena (PbS), chalcopyrite (CuFeS2), and sphalerite (ZnS).

2. **Understand Froth Flotation Process**: The froth flotation process is a method used for the concentration of ores. It involves the separation of hydrophobic materials from hydrophilic ones, where the ore is mixed with water and chemicals to create a froth that selectively collects the desired minerals.

3. **Identify a Sulphide Ore Not Concentrated by Froth Flotation**: One example of a sulphide ore that is not concentrated by the froth flotation process is **cinnabar (HgS)**.

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