Amphiboles are double chain silicate minerals that occur in a wide range of environments in igneous and metamorphic rocks. They can crystallize in either orthorhombic or monoclinic crystal systems, with those containing calcium and sodium always being monoclinic. Amphiboles are characterized by their prismatic habit, vitreous luster, and two cleavage sets. They range from black to brown in color and are translucent with densities from 2.9 to 3.5. Optically, amphiboles are anisotropic, pleochroic from green to brown, and exhibit moderate birefringence under crossed polars.

1. PHYSICAL AND OPTICAL
PROPERTIES
OF AMPHIBOLE
Shankar Lamani
223102024

2. AMPHIBOLE
 Amphibole are double chain silicate minerals.
 Members of the amphibole group of minerals occur in a wide range of
pressure, temperature environment and are common constituents of both
igneous and metamorphic rocks.

3. General formula
 W 0-1 X2 Y5 Z8 O22 (OH)2 ➢ W = 𝑁𝑎+,𝐾+
 ➢ X = 𝐶𝑎2+, 𝑁𝑎2+, 𝐾+, 𝑀𝑔2+, 𝐹𝑒2+, 𝑀𝑛2+
 ➢ Y= 𝑀𝑔2+, 𝐹𝑒2+, 𝐹𝑒3+, 𝐴𝑙3+, 𝑇𝑖4+, 𝑀𝑛2+, 𝐶𝑟3+, 𝐿𝑖+,𝑍𝑛2+
 ➢ Z= 𝑆𝑖4+, 𝐴𝑙3+
 ➢ OH may be replaced by 𝐹−, 𝑂2−

4.  The amphiboles crystallise in one of the two crystal systems:
 ➢ Orthorhombic and
 ➢ Monoclinic.
 ➢ Those in which Ca and Na are almost absent may crystallise either in
orthorhombic or in the monoclinic system; but
 ➢ Those containing Ca, Na etc. are always monoclinic.
 ➢ The most prominent elements commonly constituting an amphibole
composition are Ca, Na, Si, Al, Mg, Fe2+, Fe3+ etc.

5. Physical Properties
 Habit: Prismatic
 Color: Black
 Streak: white
 Lusture: Vitreous
 Diaphinity: Translucent
 Cleavage: 2 Sets
 Fracture: Uneven
 Hardness: 5-6
 Specific gravity: 2.9-3.5
 Uses : Industrial uses

6. Optical Properties
PPL BXP
Relief: Medium Anisotropic
Pleochroism: Green to brown Oblique extinction
Cleavage: 1 set Birefringence: Moderate
Form: Elongated Interference: 2nd and 4rth order

7. Thank You