The form of carbon which is known as black lead is ___________

Explanation

The form of carbon which is known as black lead is **graphite**.

### Step-by-Step Solution:

1. **Identify the Question**: The question asks for the form of carbon that is referred to as "black lead."

2. **Understand Carbon Forms**: Carbon exists in several forms, commonly known as allotropes. The most notable forms include graphite, diamond, and fullerenes.

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