Final answer:
Tephra that is 3mm in size is classified as lapilli. It falls between volcanic ash, which is under 2mm, and volcanic bombs, which are over 64mm.
Step-by-step explanation:
Tephra is a general term for volcanic materials ejected from a volcano during an eruption. These materials can range in size from tiny ash particles to large bombs. Specifically, tephra that is 3mm in size is called lapilli. This classification falls between volcanic ash, which refers to fragments of rock, minerals, and volcanic glass created during volcanic eruptions and measuring less than 2 mm in diameter, and volcanic bombs, which are larger than 64 mm in diameter.