"Organic rocks" is not a standard geological term. However, it's likely you're referring to sedimentary rocks that are formed from the accumulation and lithification (transformation into solid rock) of organic matter.

Here's a breakdown:

* Organic matter: This refers to the remains of living organisms, like plants, animals, and microorganisms.

* Sedimentary rocks: These rocks are formed by the accumulation of sediments, which are loose materials like sand, mud, and organic matter.

Here are some examples of rocks that are formed primarily from organic matter:

* Coal: Formed from the accumulation of plant matter in swamps and bogs.

* Oil shale: Contains a significant amount of kerogen, which is a type of organic matter that can be converted into oil and gas.

* Limestone: Although primarily composed of calcium carbonate, some limestone formations are rich in organic matter, like fossils.

* Diatomite: Formed from the accumulation of diatom skeletons, which are microscopic algae with silica shells.

It's important to note that most sedimentary rocks contain some amount of organic matter, even if it's not the primary component. However, the rocks listed above are those where organic matter plays a significant role in their formation and composition.