Final answer:
A solid mineral body enclosed within a diamond is known as an included crystal. Included crystals are minerals or rock fragments that became encapsulated by the diamond as it formed. These inclusions can affect a diamond's clarity and value.
Step-by-step explanation:
A solid mineral body enclosed within a diamond (or other gem) is referred to as an included crystal. This term describes a crystal or crystalline fragment of a mineral or rock that has been enclosed within another mineral or rock at the time the host was forming.
The formation of diamonds involves each carbon atom forming four single bonds to four other atoms at the corners of a tetrahedron (sp³ hybridization). This configuration leads to the creation of an extremely strong three-dimensional network, making the diamond the hardest known natural substance, famed for its hardness and high melting point.
The presence of an included crystal does not typically affect the structural integrity of the diamond, but it can impact the clarity and thereby the value of the gemstone.