Hornblende

HornblendePhysical Properties (1)

Group Silicates-Inosilicates

Color Green, Black

Crystal Habit Prismatic

Crystal System

Monoclinic

Cleavage Perfect

Fracture Uneven, Brittle

Hardness 5-6

Luster Vitreous

Streak White to Gray

Specific Gravity

3.1-3.3

Transparency Translucent to Opaque

Optical Properties (3 & 7)

Birefringence Ranges from .018 to .028

Interference Colors

Shades of green, yellow , and brown

Extinction Angle Symmetrical to cleavage

Index of Refraction

Nα: 1.60-1.70Nβ: 1.61-1.71Nγ : 1.62-1.73

Pleochroism Green or brown

Optic Sign Optically negative or positive

2V Angle Ranges from 52 degrees to 85 degrees

Twinning Simple and lamellar twinning

Relief High positive relief

History of HornblendeThe discovery of hornblende is not exactly known, however amphiboles (the group of minerals hornblende belongs to) was discovered in 1801 by French mineralogist René-Just Haüy (2). Hornblende got its name from the German word horn and blenden, which means to blind or to dazzle. The meaning of the name is any dark prismatic mineral that occurs in ores, but does not contain any recoverable metals (2).

Uses of HornblendeUsed for decoration and as a hand sample (6).

OccurrenceHornblende is an important mineral in the rock formation of igneous and metamorphic rocks (6). Hornblende is the most common amphibole (6).Two end member hornblendes that exist are ferrohornblende and magnesiohornblende, both are calcium rich (1).

We can use amphiboles (Such as Hornblende) to help identify an unknown igneous rock (8).

References1. Bonewitz, Ra, Margaret W. Carruthers, and Richard Efthim. Rock and Gem. New York: DK Pub., 2008. Print.2. Holden, Martin. The Encyclopedia of Gemstones and Minerals. New York: Facts on File, 1991. Print.3. "Hornblende." Clark Science Center - Smith College. Web. 06 Dec. 2010.

<http://www.science.smith.edu/departments/Geology/Petrology/Petrography/Hornblende/Hornblende.html>.

4. "Hornblende Mineral | Uses and Properties - GEOLOGY.COM." Geology.com - Earth Science News, Maps, Dictionary, Articles, Jobs. Web. 06 Dec. 2010. <http://geology.com/minerals/hornblende.shtml>.

5. "Igneous Minerals Image Gallery." Jeffrey_C._Reid_Forensic_Geology. Web. 06 Dec. 2010. <http://www.jeffreycreid.com/petrography/pet_igneous.html>.

6. Klein, Cornelis, Barbara Dutrow, James Dwight Dana, and Cornelis Klein. The 23rd Edition of the Manual of Mineral Science: (after James D. Dana). Hoboken, NJ: J. Wiley, 2008. Print.

7. Nesse, William D. Introduction to Optical Mineralogy. New York: Oxford UP, 2004. Print.8. "GSCI 100 Lecture #27 - - Fall 2010." Index of /. Web. 06 Dec. 2010.

<http://hays.outcrop.org/GSCI100/lecture27.html>.9. "File:René Just Haüy.jpg." Wikimedia Commons. Web. 06 Dec. 2010.

<http://commons.wikimedia.org/wiki/File:René_Just_Haüy.jpg>. 10. Doodle's Fine Quartz and Minerals. Web. 06 Dec. 2010. <http://www.finequartz.com/cgi-bin/index.pl?

str=Hornblende&ptr=0>. 11. "Ferrohornblende Image." Mineralogy Database. Web. 06 Dec. 2010.

<http://webmineral.com/specimens/picshow.php?id=398&target=Ferrohornblende>. 12. "Magnesiohornblende Image." Mineralogy Database. Web. 06 Dec. 2010.

<http://webmineral.com/specimens/picshow.php?id=704&target=Magnesiohornblende>.

Chemical Composition: (CA,Na)2-3 (Mg, Fe, Al)5, Si6, (Si,Al)2, O22 (OH)2

Composition And Crystal Structure: Hornblende can be divided into two end members, ferrohornblende and magnesiohornblende, both are calcium rich (1). Hornblende is monoclinic and 2/m (6).Can have two prisms and one pinacoid, or three prisms and two pinacoids (6).

This image shows one of Hornblende’s end members, ferrohornblende (11).

This image shows one of hornblende’s end members,magnesiohornblende (12).

These images show rare example or hornblende crystals ( & 10).

French Mineralogist René-Just Haüy (9)

Hornblende’s crystallographic axes (7)

This is hornblende in a thin section and in PPL (Plain Polarized Light) (3).

This image shows Hornblende’s 60°/120° cleavage (3)

This thin section image shows hornblende in XPL (Cross Polarized Light) (3).

This thin section image shows Hornblende’s twinning (5)

http://www.science.smith.edu/departments/Geology/Petrology/Petrography/Hornblende/Hornblende.html

http://www.nps.gov/blca/naturescience/schist.htm

http://www.wpclipart.com/rocks_minerals/A/Am/Amphibole_Hornblende__Igneous_rock.png.html

Hornblende Like the essential building block of plagioclase, hornblende is actually a member of the solid solution series for amphiboles. Hornblende is the most common occurring amphibole in the canyon and is black or dark green in color. When it fractures, it tends to break at angles of either 60 or120 degrees. It contains significant amounts of potassium and fluorite in its chemical formula, which helps determine the color of the mineral.It sometimes forms large masses known as amphibolite or hornblende schists that are made up of thin, black parallel aligned, needle-like crystals.It is difficult to find any large individual crystals.The name comes from the German miner's term "horn" possibly in reference to the color of horn and "blenden" which means to deceive. This seems to have come from the fact that the mineral mimics the more valuable metallic ores, but doesn't produce a commercial viable metal.Hornblende makes up one of the types of schists in the canyon.