Allotrope of carbon used in cutting glass and rock drilling.

Explanation

**Step-by-Step Solution:**

1. **Understanding Allotropes of Carbon:**
- Carbon has several allotropes, which are different forms of carbon that have distinct physical properties. The most common allotropes include graphite, diamond, and fullerenes.

2. **Identifying the Allotropes Used in Cutting:**
- Among these allotropes, we need to identify which one is specifically used for cutting glass and drilling rocks.

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