Rock Definitions

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Petrified Wood

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Another name for wood fossils or fossilized wood. Trees fossilize under the right conditions, if they are covered by earth, sand, or volcanic ash before they rot. Water seeps through the covering earth and soaks into the wood. The water has minerals in it. Wood has many tiny holes. The minerals fill these holes and become solid after many millions of years. This is petrification.

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Plant Leaf

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Plant Leaf fossils are less common than animal fossils. Leaves and other plant parts break down quickly under normal conditions. They can be preserved if they are quickly buried in the sediment of a lake or pond.

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Ammonite

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A type of cephalopod that appeared in the fossil record in during the Devonian Era. They are related to squid and octopus. The nautilus is their closest living relative. The ammonite shell had sections, with the living animal occupying only the section of the closest to the head. As the soft-bodied ammonite got larger, it grew a new shell section and sealed off the old one with a layer called septa. All ammonites became extinct 65 million years ago.

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Brachiopod

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Bivalves that live on the ocean floor. They are found in today's oceans and have a history dating back over 500 million years. Because of this are considered to be living fossils. Brachiopods are filter feeders, getting their nourishment from tiny organisms floating in ocean water. They are related to bryzoans.

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Trilobites

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Trilobites are an ancient form of arthropods. Trilobites had many life styles; some moves over the sea bed as predators, scavengers or filter feeders and some swarm, feeding on plankton.

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Ammonite

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Marble

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Marble is made from when limestone(s) or dolostone(s) are put under heat and pressure. It is usually white in color with swirls of black throughout.

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Slate

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Slate is formed from shale(s) that has been put under heat and pressure.

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Gneiss

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This rock is identified by its minerals having formed visible banding and does NOT have a lot of mica (platy minerals).

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Quartzite

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Quartzite is made when sandstone(s) high in quartz is put under heat and pressure.

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Limestone

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Limestone is a Biochemical Sedimentary Rock that is formed organic processes from living organisms producing sediments. Living organisms can be snails and clams whose discarded calcium carbonate shells from limestone.

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Coal

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Coal is a Biochemical Sedimentary Rock that is formed organic processes from living organisms producing sediments. Coal formation begins when thin layers of silt covers plant material that died and fell in a swamp or bog.

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Lignite Coal

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Lignite Coal is a Biochemical Sedimentary Rock that is formed organic processes from living organisms producing sediments. Coal formation begins when thin layers of silt covers plant material that died and fell in a swamp or bog. Each year, new layers of plant material falls into the swamp until the weight of the overlying sediments drives the water out forming a loose, crumbly material called peat. It then hardens to form Lignite Coal.

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Bituminous Coal

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Bituminous Coal is a Biochemical Sedimentary Rock that is formed organic processes from living organisms producing sediments. Coal formation begins when thin layers of silt covers plant material that died and fell in a swamp or bog. Each year, new layers of plant material falls into the swamp until the weight of the overlying sediments drives the water out forming a loose, crumbly material called peat. It then hardens to form Lignite Coal and Lignite Coal hardens to form Bituminous Coal (which is used to make steel).