Minerals, Igneous, Sedimentary, Metamorphic Rocks Flashcards
Crystal form (habit)
the general shape or character of a crystal or cluster of crystals that have grown in nature unimpeded.
Cleavage
breakage of a mineral along a flat plane of weakness
Excellent Cleavage
easily identifiable; minerals that when broken produce pieces shaped as cubes, rhombohedrons, columns, pyramids or planes
Good Cleavage
minerals that when broken retain a distinctive shape with flat sides, but have distortion around parts of the mineral (ex: rounded edges)
Poor/Absent
.
Mineral Hardness
measure of the resistance of a mineral to abrasion or scratching
Color
Not always diagnostic because of impurities
Streak
Color of the fine powder of a mineral obtained by rubbing the mineral across a piece of unglazed porcelain
Reaction to Hydrochloric Acid
determines whether a mineral is a member of the Carbonate family (CO3)
Rocks
aggregates of minerals in which the minerals retain their individual properties
Igneous Rocks Compositional Features
- Dominated by dark colored silicate minerals
- ~50% dark to ~50% light colored silicate minerals
- Dominated by light colored silicate minerals
Igneous Rocks Grain Size
Usually have visible crystal. Fine grain = extrusive rock. Coarse grain = intrusive rock
Felsic
Igneous rock composed mainly of light-colored minerals like quartz and feldspar
Intermediate
Igneous rock composed of a mixture of light and dark-colored minerals like quartz, feldspar, amphibole, and biotite
Mafic
Dark-colored minerals like olivine, pyroxene, and amphibole account for 45%-85% of the rock. Plagioclase feldspar makes up most of the rest of the rock.
Sedimentary rocks
rocks composed of sediment-products of weathering consisting of loose rock fragments, mineral grains broken down from once-intact rock, mineral crystal that precipitate directly out of water, as well as shells and skeletons of organisms.
Clastic rocks
composed of cemented particles that have been subjected to moderate to intense physical and chemical weathering
Chemical rocks
Chemicals rocks are all created through some form of dissolution and precipitation, the result of chemical result weathering of surface rocks and minerals. Composed on one mineral, unlike Clastic rocks.
Biochemical
precipitates are produced from the hard skeletal tissue of once living organisms
Clastic Coarse Grained
Conglomerate (rounded) … Breccia (angular)
Clastic Medium Grained
Quartz Sandstone. Arkose Sandstone. Lithic Sandstone.
Fine Grained
Mudstone. Shale.
Chemical Limestone
- Large shells frag . (Coquina)
- Mixed-Sized Shell and Skeletal Material (fossiliferous)
- Smooth and fine grained (Micrite)
- Powdery (Chalk)
- Ooids (oolitic); Pisoids (Pisolitic)
- Crystalline
Chemical Not Limestone
- Rusty (ironstone)
- Powdery (claystone)
- Very soft (alabaster)
- Very hard (chert)
- Salt (rock salt)
- Black, Dusty, light (Coal)
Foliation
refers to a metamorphic texture in which flat or elongate minerals are preferentially aligned in response to exposure to high temperatures and differential stress in a high pressure environment (look for parallel lines / directionality)
Non-Foliated Rocks
show fused-together grains, which are created by a process called ‘recrystallization’, in which the atoms of the original, individual grains, break their bonds and the re-bond as one entity, forming a mosaic-type texture
Types of luster
Metallic
Non-metallic
Vitreous or glassy
Pearly
Resinous
Earthy
Types of luster
Metallic
Non-metallic
Vitreous or glassy
Pearly
Resinous
Earthy
Hardness of Common Objects
Fingernail = 2 to 2.5
Nail = 4
Glass = 5.5
Streak plate = 6.5 to 7
