Indigo Gabbro

Indigo Gabbro

Gabbro includes a lot of different silicate crystals that are dark in color and full of tiny crystals that are still large enough to be seen by the naked eye.  Gabbros is igneous (think ignite and fire) in that it forms as lava cools and crystalizes while trapped beneath the Earth's surface which means it cools and solidifies more slowly.  That is why larger "grains" of crystal are visible.