A Conversation About Marble

Student: Where does marble come from?
Teacher:  Marble comes from limestone. You could say it’s a “newer” limestone.

S: What? Marble is really just a ‘newer’ limestone?T: Yes. According to the Vermont Marble Company, “the original sedimentary limestones were formed in an ancient seaway, mainly from the remains of marine organisms and lime muds resulting from chemical precipitation. These original sediments consolidated, forming coherent rocks termed “limestones.”

S: Oh, that’s why often there are a little bit of shells, fossils and mud in some limestones.
T: That’s right. 

S: Well, how did limestone become marble? 
T: “Subsequent heat, pressure and hydrothermal solutions brought on by a period of earth movements, resulted in the extensive deformation of the limestone beds and a re-crystallization that produced the highly crystalline character of commercial marble.”

S: Ah ha. That’s why marble is tighter grained (harder) and shinier.
T: Yes. Basically, marble is a metamorphic rock resulting from recrystallization of limestone.

S: You mean marble is a newer limestone.
T: (Sigh.) Yes.