Staurolite

Definition

Staurolite is a brown to black mineral that is primarily composed of iron, aluminum, and silicate, and is known for its characteristic cross-shaped crystals. This mineral typically forms under high-grade metamorphic conditions and is often found in schist and gneiss, making it significant in understanding metamorphic processes and rock formation.

5 Must Know Facts For Your Next Test

1. Staurolite commonly forms in metamorphosed shale or mudstone, indicating a history of significant pressure and temperature during its formation.
2. The name 'staurolite' is derived from the Greek word 'stauros,' meaning 'cross,' which refers to the unique cross-shaped twinning of its crystals.
3. Staurolite can be an important indicator of the metamorphic conditions of the surrounding rocks, as its presence often suggests a specific range of temperatures and pressures.
4. In addition to its geological significance, staurolite is sometimes used as a gemstone due to its unique appearance and crystal formations.
5. The occurrence of staurolite can often be associated with the presence of other metamorphic minerals such as garnet and kyanite in the same rock formations.

Review Questions

• How does staurolite's crystal structure relate to its formation conditions and what does this indicate about the geological environment?
  • Staurolite's distinctive cross-shaped crystals indicate a specific crystallization process that occurs under high-pressure and high-temperature conditions typical of regional metamorphism. This crystal structure reflects the environmental conditions during its formation, which often involves the alteration of parent rocks like shale. The presence of staurolite in a rock can suggest that it underwent significant metamorphism, revealing important information about the tectonic processes at play.
• Discuss the role of staurolite in identifying the metamorphic history of rocks and how it contributes to our understanding of regional geology.
  • Staurolite serves as a key indicator mineral for metamorphic geologists because its stability is confined to specific pressure-temperature conditions. By analyzing staurolite in a rock sample, geologists can infer the grade of metamorphism that the rock has experienced. This information aids in reconstructing the geological history of an area, helping to map out past tectonic events and changes in environmental conditions during metamorphism.
• Evaluate the significance of staurolite in both practical applications, such as gemstone use, and scientific research regarding metamorphic processes.
  • Staurolite holds both aesthetic value as a gemstone and practical importance in scientific research. As a gemstone, it is appreciated for its unique appearance and is sometimes used in jewelry, offering insights into mineral appreciation. Scientifically, staurolite plays a crucial role in understanding metamorphic processes; its presence can reveal information about historical tectonic activity and environmental conditions. Evaluating staurolite helps bridge the gap between mineralogical studies and practical applications, highlighting its multifaceted significance.

Related terms

Metamorphism:

The process by which rocks undergo changes in mineralogy, texture, and chemical composition due to changes in temperature and pressure.

Schist:

A medium to high-grade metamorphic rock characterized by well-aligned minerals, often including mica, quartz, and garnet.

Gneiss: A high-grade metamorphic rock distinguished by its banded appearance, resulting from the segregation of mineral constituents into distinct layers.