These stones are formed when the magma from the earth cools inside the earth or on the earth surface.
A. Intrusive - subsurface crystallization
B. Extrusive- above surface crystallization
*note Temperature and time has alot of effect on crystal sizes i.e.: Heat + time = Larger crystal
Igneous form occurrence below ground presents itself in 2 basic ways:
Intrusive basic dike, which is like having layers of cardboard over your head and punching your fist up into it. Plutonic, this is like a huge hot ball of stone burning its way around deep below the surface and it usually has "hot arms" that reach out from its main mass. Crystal habit can successfully delineate a Igneous stones origin, usually. Dikes are cooler thus forming smaller crystals and Plutons are hotter thus forming larger crystals.
C. Mineral content
D. Grain size, Plutonic >3/16" coarse. Extrusive 1/64" - 3/16" Medium and < 1/64" fine
E. Crystal shape
F. Texture % A, %B, crystal angle.
A. Acid rocks > 65% Si + > 10% Modal Quartz
B. Intermediate rocks 55% - 65% Si
C. Basic rocks 45% - 55% Si < 10% Modal Quartz
D. Ultra-Basic < 45% Si.
|Introduction and Selection of stones||Stone Mortars|
|Properties and Tests on Stones||Design and Construction of stone buildings|
|Applications of Stones||Atterberg's Limits|