Common Mineral Questions

Rocks versus minerals

Photos by Lauren Duguid/ANS

Treasures From the Mineral Vault opens this Saturday, November 5! This intimate exhibit features nearly 50 minerals from the Academy’s famous collection. Straight from a real vault, the specimens glitter with other-worldly colors, varied shapes and forms, and the ability to convey the awesome force and output of our planet.

View minerals of vivid yellow, forest green, deep red, and radiant purple, and discover how they were formed millions of years ago deep within the earth. Find out why some minerals sparkle and others are shaped like cubes and prisms. Learn the difference between a rock and a mineral. From varieties of quartz to calcite, fluorite, and feldspar, the Academy’s minerals take the stage—some for the first time in decades.Orange, green, and variegated minerals on a black background

Here’s a sneak peak at some common questions about these rare treasures:

What are minerals? How are they different from rocks?

Minerals are specific chemical compounds found in nature, often formed deep within the earth. Rocks are aggregates of one or more minerals that are tightly compacted together.

petrified wood on a black background as part of the mineral collection at the Academy of Natural SciencesWhy do different minerals have different shapes?

It all comes down to atoms. Each mineral’s atomic structure is arranged in predictable, three-dimensional geometric patterns. When repeated, crystals grow larger following the same geometric pattern, forming the distinctive shapes for each mineral.

Why do minerals have different shapes? Orange sparkling mineral on black background from the mineral vault at the Academy of Natural SciencesWhy do some minerals sparkle?

Light interacts with the surfaces of minerals in different ways. Sparkling minerals are often vitreous (glassy) or adamantine (diamond-like) with hard, reflective surfaces. They are usually clear or translucent, allowing light to bounce off the surface as well as through the crystals. The greater the number of surfaces (natural or man-made), the greater the sparkling effect.

Why do minerals sparkle? A green sparkling mineral from the vault at the Academy of Natural Sciences.How can the same mineral be so many colors?

When light strikes an object, it reflects certain wavelengths of light back to our eyes, which is how we see its color. If an object appears green, it is reflecting green light and absorbing all the other wavelengths.

A mineral’s structure and chemical composition give it a characteristic color (or sometimes no color at all). Some color shifts are due to trace elements like copper. Other color variations come from structural aberrations in the crystals.How can a mineral be so many different colors? Purple and white mineral on black background from mineral collection at Academy of Natural Sciences.

Treasures From the Mineral Vault  is free with general admission. Check it out today to see these and other beautiful minerals rarely on display to the general public.

buy tickets to the Academy of Natural Sciences