(Click on the picture to return to Rock Type Lab key)
This is the same material that underlies most of the world's ocean floors. Its dark color indicates a relatively high proportion of ferromag (iron- and magnesium-bearing) minerals.
This rock has numerous VERY tiny gas bubble cavities on its surface. It does not react with hydrochloric acid.
N. C. Heywood maintains this page, last updated 10NOV99.