What is the difference between dark and light silicate?

There are more differences between dark and light silicate than just their color. Light silicate is nonferromagnesian, while dark silicates are ferromagnesian. Light silicate is also lighter in gravity at about 2.7, and they usually contain bits of calcium, sodium, potassium and aluminum. Dark silicate usually has a heavier gravity between 3.2 and 3.6, and they are mostly comprised of magnesium and iron.