What is a hornblende schist?
What is a hornblende schist?
Hornblende schist, for example, is a variety of schist rich in the amphibole mineral hornblende, though the rock may also contain an abundance of plagioclase feldspar and other substances as well. It is widely distributed in igneous and metamorphic rocks, such as schists.
What is the cleavage of hornblende?
| Hornblende | |
|---|---|
| Cleavage | Imperfect at 56° and 124° |
| Fracture | Uneven |
| Mohs scale hardness | 5–6 |
| Luster | Vitreous to dull |
What is amphibole?
Amphibole (/ˈæmfɪˌboʊl/) is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain SiO. 4. tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures.
Is hornblende a crystal?
hornblende, calcium-rich amphibole mineral that is monoclinic in crystal structure. Hornblende’s generalized chemical formula is (Ca,Na)2(Mg,Fe,Al)5(Al,Si)8O22 (OH)2. Hornblendes exhibit typical amphibole structures; these are based on double tetrahedral chains between which four metal sites are located.
Is hornblende a pleochroic?
Hornblende is generally pleochroic, often in shades of green, blue, brown, and less commonly red or yellow. This example is in shades of green only, but brown hues are generally more common.
Is Tourmaline an amphibole?
The name amphibole (Greek αμφιβολος – amphibolos meaning ‘ambiguous’) was used by René Just Haüy to include tremolite, actinolite, tourmaline, and hornblende. The group was so named by Haüy in allusion to the protean variety, in composition and appearance, assumed by its minerals.
Where can hornblende be found?
Hornblende is the most common of the clinoamphiboles. Hornblende is commonly found in metamorphic rocks such as schists and gneisses, and igneous rocks such as diorites and dacites.
How do you identify apatite in the thin section?
Due to the phosphate content, apatite crystals are usually small and can be hard to detect in thin section. The apatite crystal is very small and elongated. Its high relief allows it to stick out from the other colorless minerals. Under cross-polars apatite exhibits a first order gray color.
