My Blog

Schist is a metamorphic rock with well-developed foliation. It often contains significant amounts of mica which allow the rock to split into thin pieces. It is a rock of intermediate metamorphic grade between phyllite and gneiss. The specimen shown above is a “chlorite schist” because it contains a significant amount of chlorite. It is about two inches (five centimeters)…

Quartzite is a non-foliated metamorphic rock that is produced by the metamorphism of sandstone. It is composed primarily of quartz. The specimen above is about two inches (five centimeters) across.

Phyllite is a foliated metamorphic rock that is made up mainly of very fine-grained mica. The surface of phyllite is typically lustrous and sometimes wrinkled. It is intermediate in grade between slate and schist. The specimen shown above is about two inches (five centimeters) across.

Novaculite is a dense, hard, fine-grained, siliceous rock that breaks with a conchoidal fracture. It forms from sediments deposited in marine environments where organisms such as diatoms (single-celled algae that secrete a hard shell composed of silicon dioxide) are abundant in the water. The specimen shown above is about three inches across.

Mariposite is a word that has been used in many ways. It can refer to green mica minerals, or metamorphic rocks that contain enough green mica to impart a green color. Gold prospectors learned that gold could be found in areas where these green rocks were present. This is because mariposite is an ore of gold.

Marble is a non-foliated metamorphic rock that is produced from the metamorphism of limestone or dolostone. It is composed primarily of calcium carbonate. The specimen shown above is about two inches (five centimeters) across.

Mariposite is a word that has been used in many ways. It can refer to green mica minerals, or metamorphic rocks that contain enough green mica to impart a green color. Gold prospectors learned that gold could be found in areas where these green rocks were present. This is because mariposite is an ore of gold.

Hornfels is a fine-grained nonfoliated metamorphic rock with no specific composition. It is produced by contact metamorphism. Hornfels is a rock that was “baked” while near a heat source such as a magma chamber, sill, or dike. The specimen shown above is about two inches (five centimeters) across.

Lapis Lazuli, the famous blue gem material, is actually a metamorphic rock. Most people are surprised to learn that, so we added it to this photo collection as a surprise. Blue rocks are rare, and we bet that it captured your eye. The round objects in the photo are lapis lazuli beads about 9/16 inch…