Curated category
Sedimentary rocks
- Conglomerate (geology)A pile of rounded gravel sits surrounded by finer sand and clay at Point Lobos. This mixture forms a rock known as conglomerate.
- GypsumA hand can bend a crystal of gypsum under its own pressure. This physical trait defines the mineral on the Mohs scale as having a hardness value of 2.
- CoalThe late Carboniferous period, spanning roughly 359 to 299 million years ago, witnessed the rise of vast wetlands that would eventually become today's coal…
- Oil shaleOil shale is an organic-rich fine-grained sedimentary rock containing kerogen, a solid mixture of organic chemical compounds.
- FlintA piece of flint long and weighing 171 grams sits on a table. This sedimentary cryptocrystalline form of quartz occurs as nodules within chalk or marly…