When it comes to minerals especially gemstones (precious, semi-precious or otherwise) and fossils there are many common terms that can help you identity what you may be looking to purchase or find. Here is a list of those common terms that could help:
Alluvial deposit particles of sediment or other material deposited by a running body of water
Breccia sedimentary rock made up of medium sized angular fragments that have been bonded together with natural cement
Carboniferous geological time period that stretches approximately from 290 - 365 million years ago
Clast small fragment of rock that has been broken or eroded off a larger piece
Cleavage characteristic property of some rocks and minerals that come apart along distinct parallel planes
Conglomerate sedimentary rock made up of pieces of rocks that have been worn into rounded shapes and then bonded together with natural cement
Cretaceous geological time period that stretches approximately from 65 145 million years ago
Devonian geological time period that stretches approximately from 360 - 415 million years ago
Dyke intrusion of igneous rock that is typically vertical or steeply inclined
Foliation - rock structure that is composed of small platy mineral such as clay
Fossil remains of animal or plant that has been preserved in rock
Gneiss high grade metamorphic rock formed from igneous or sedimentary materials
Igneous rocks type of rock that is formed by the cooling of intrusive or extrusive magma
Intrusion formation of igneous rock that has forced its way into pre-existing rocks
Jurassic geological time period that stretches approximately from 145 200 million years ago
Lava molten material which is expelled by a volcanic eruption
Lithified - process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock
Magma molten material that forms igneous rocks when it cools
Massive bulk form of rock or mineral
Matrix fine material which fills the voids in the coarse grained cemented structure
Metamorphic rocks - igneous or sedimentary rocks that have "morphed" into another kind of rock
Mica complex series of shiny minerals with a flexible, platy structure and perfect cleavage
Mudstone sedimentary rock that is composed of fine grained particles
Pegmatite very coarse grained igneous rock
Permian geological time period that stretches approximately from 250 300 million years ago
Pyroclastic pieces of material that have been thrown up as the result of volcanic activity
Sandstone sedimentary rock that is mostly composed of sand sized quartz grains
Schist medium grade metamorphic rock that is mostly composed of elongated minerals
Sediment a particulate material that has settled out of suspension in still water
Sedimentary rocks rocks that are composed of sediments that have been compacted and lithified
Shale soft, fine grained layered sediment rock composed of compacted sediments
Sill intrusion of igneous rock similar to a dyke in a roughly horizontal orientation
Silt fine sediment that has a particle size between those of sand and mud
Siltstone fine grained sedimentary rock that is composed of particles with seizes between those of sand and mud
Slate metamorphic rock with a fine grain that is formed from shale or mudstone
Tuff rock that is mostly composed of volcanic ash
Vein - a crack in a rock that has been filled with a solid material composed of crystal and/ or mineral
Vug - cavities inside rock mostly that may be partially filled with quartz, calcite, and other secondary minerals