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Rocks
Basalt
Chert
Marl
Sedimentary Rock
- Crossbedding
Limestone

Rocks of Galveston Bay

Basalt	Chert This is a sedimentary mineral precipitate of quartz. Chert was used by American Indians to make arrow heads. Also known as flint.
Marl This limestone is from Beaumont. A common clam found in marl is the dwarf surf clam. Marl was formed 10,000 - 15,000 years ago.	Sedimentary Rock Crossbedding
Limestone Limestone is usually not used to build a jetty because marine organisms attack the rock.