Density: This refers to the mass of a substance per unit volume. It's a more precise scientific term than "heaviness" and is commonly used to describe rocks and minerals.
Massive: This term describes something that is very large and heavy. It's often used to describe large rock formations or geological features.
Dense: This is a more general term that can be used to describe something that is packed tightly together, which often implies heaviness.
Weighty: This term is more common in general language and less specific to geology.
Specific Gravity: This term refers to the ratio of the density of a substance to the density of water. It's a valuable tool for identifying minerals.
Ultimately, the best adjective to use will depend on the specific context and what you want to emphasize.