264 



EXPLORATION GEOPHYSICS 



if a large thickness of diatomaceous shale is present at considerable depth; 

 and (3) if a thick section of limestone or anhydrite overlies a thick section 

 of sands, shales, clay marls or other poorly consolidated materials. 



TABLE 7. 



DENSITIES OF VARIOUS CONSTITUENTS OF THE 

 EARTH'S CRUST t 

 TYPE OF MATERIAL 



Igneous Rocks Normal Range Mean 



Pyroxenite 3.10-3.32 3.23 



Peridotite 3.15-3.28 3.23 



Gabbro 2.85-3.12 2.98 



Norite 2.72-3.02 2.98 



Diabase 2.80-3.11 2.97 



Diorite 2.72-2.96 2.84 



Quartz Diorite 2.68 - 2.96 2.81 



Syenite 2.63 - 2.90 2.76 



Granodiorite 2.67-2.79 2.72 



Anorthosite 2.64-2.92 2.73 



Granite 2.52-2.81 2.67 



Extrusive Rocks 



Basalt 2.7-3.3 3.0 



Lava 2.8-3.0 2.9 



Andesite 2.4-2.8 2.6 



Dacite 2.4-2.8 2.6 



Trachyte 2.4-2.8 2.6 



Phonolite 2.5 -2.7 2.6 



Rhyolite 2.4 -2.7 2.55 



Vitrophyre 2.4 -2.5 2.45 



Obsidian 2.2-2.4 2.3 



Metamorphic Rocks 



Amphibolite 2.9 -3.0 2.95 



Phyllite 2.7 -2.8 2.75 



Gneiss 2.6-3.0 2.8 



Slate 2.7 -2.9 2.8 



Marble 2.6 -2.9 2.75 



Graywacke 2.6 - 2.7 2.65 



Schist 2.4 -2.9 2.65 



Serpentine 2.4 - 2.8 2.6 



Quartzite 2.5 - 2.6 2.55 



Rock Forming Minerals 



(Salic Minerals)* 



Zircon 4.0 -4.9 4.45 



Corundum 3.9 -4.0 3.95 



Anorthite 2.7 -2.8 2.75 



Albite 2.6 -2.7 2.65 



Nepheline 2.6 - 2.7 2.65 



Quartz 2.5-2.7 2.6 



Orthoclase 2.5 -2.6 2.55 



Leucite 2.5 - 2.5 2.5 



(Femic Minerals)** 



Hematite 4.9-5.3 5.1 



Magnetite 5.0-5.2 5.1 



Ilmenite 4.4 -4.9 4.65 



Hypersthene 3.3 - 3.5 3.4 



f The data given here represent typical averages. Wide variations may occur. 

 * Mnemonic for siliceous, aluminous. 

 ** Mnemonic for ferric or ferrous magnesian. 



