Cochise College          Photos of Minerals

                          Geology Home Page                

                          Roger Weller, geology instructor

                          wellerr@cochise.edu
                                  copyright 2007-R.Weller
 

Mineral Information on:
tourmaline


Chemical Group:    silicate

Chemical Formula: 
Na(Mg,Fe)3Al6(BO3)3(Si6O18)(Si6O18)(OH)4

Color: black, brown, dark blue, colorless, pink, red, green, blue and even multicolored

Streak:  white                Luster:  vitreous

 

Hardness:  7.5            Specific Gravity:   3.0 to 3.2              Fracture:  conchoidal

Cleavage: poor            Special Properties: strongly pyroelectric and piezoelectric

 

Crystal Forms: Trigonal system
     Tourmaline forms long prismatic 3-sided crystals, capped with basal pinacoid.
     Crystals are often striated along their lengths.

Mineral Associations: tourmaline is found in pegmatites and metamorphosed rocks.

Identifying Characteristics:  rounded triangular cross-section of crystals

Uses: if transparent and colorful, as a gemstone

Occurrences: Brazil; in thee USA from Maine, New Hampshire, South Dakota, California

Toxicity:      when-swallowed- low         when inhaled- high

Additional Information: