Chalk is a fine-textured, earthy type of limestone distinguished by its light color, softness, and high porosity. It is composed mostly of tiny fragments of the calcite shells or skeletons of plankton, such as foraminifera 查看更多內容

Chalk is so common in Cretaceous marine beds that the Cretaceous Period was named for these deposits. The name Cretaceous was derived from Latin creta, meaning chalk.
The Chalk Group is a European stratigraphic unit deposited … 查看更多內容

Most people first encounter chalk in school where it refers to blackboard chalk, which was originally made of mineral chalk, since it readily crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be readily erased. … 查看更多內容

• Gordon, Helen (23 February 2021). "Rock of ages: How chalk made England". The Guardian. Adapted from Notes From Deep Time: A Journey … 查看更多內容

Chalk was formed in the Cretaceous Period, between 99 and 65 million years ago. It was deposited on extensive continental shelves at depths between 100 and 600 metres (330 and 1,970 ft), during a time of nonseasonal (likely arid) climate that reduced the … 查看更多內容

Chalk is mined from chalk deposits both above ground and underground. Chalk mining boomed during the Industrial Revolution, due to the need for chalk products such as quicklime and bricks. 查看更多內容

• Blackboard – Reusable writing surface
• Chalk carving
• Chalk line – Tool for marking straight lines 查看更多內容