Rock Types

Categories

Sedimentary Rocks

Sedimentary rocks are formed from pre-existing rocks that have undergone weathering (the breakdown of rock into smaller fragments caused by physical and chemical events) and transportation (moved from one location to another by wind, water, animals, etc.). Sedimentary rocks can further be categorized into three main groups based on which processes formed the rock:

  • Clastic sedimentary rocks: These result from the lithification of unconsolidated (loose) sediment. Sediment can be many different sizes, including small grains of clay and sand, up to large pebbles or cobbles. Lithification is a process that involves compaction of the sediment layers and cementation. Cementation is when water-soluble minerals fill the cracks between each individual sediment grain, gluing them all together to form a solid rock. Some examples include sandstone, conglomerate, or shale. 
  • Chemical sedimentary rocks: These rocks form when a solution is supersaturated in elements that are constituents for minerals. Given the appropriate physical conditions, minerals precipitate out of the solution and form solid rocks. Some examples include limestone, banded iron formation, or rock salt.
  • Biochemical/organic sedimentary rocks: These rocks form from the accumulation of organic debris, including remains from plants or animals. Biochemical sedimentary rocks are different from chemical sedimentary rocks because living organisms play a major role in turning the chemical constituents into solid rock. Some examples include coal, fossilized coral, or coquina.
Picture Rock Number Rock Name  Process of Formation
Jasper conglomerate
1 Jasper conglomerate Clastic
Gordon lake cherty siltstone
4 Gordon Lake cherty siltstone Clastic
Gowganda conglomerate
5 Gowganda conglomerate  Clastic
Matinada conglomerate
6 Matinenda conglomerate  Clastic
Keweenawan conglomerate
7 Keweenawan conglomerate Clastic
Jacobsville sandstone
9 Jacobsville sandstone Clastic
Banded iron formation
20 Banded iron formation (magnetite) Chemical
Siderite
21-22 Siderite  Chemical
Amabel dolostone
24 Amabel dolostone Chemical
Lockport dolostone
25 Lockport dolostone Chemical
  26-27 Dolostone with calcite Chemical
Eramosa dolostone
28 Laminated Ermosa dolostone Chemical
Potsdam sandstone
29-31 Potsdam sandstone Clastic
Columbus limestone
35 Columbus limestone Chemical
Fossil coral colony favosites
38 Fossil coral colony favosites Organic
Calcite concretions
39 Calcite concretions Chemical
Stromatolite marble
49 Stromatolite marble  Organic
Stromatolite fossils
50 Stromatolite fossils Organic
Amethyst quartz breccia
51 Amethyst quartz Breccia  Clastic
Frank slide boulder
55 Frank slide boulder Chemical
Tyndall stone
63 Tyndall stone Chemical
Anthracite coal
68 Anthracite coal Organic
Giant mine breccia
70 Shear-hosted gold lode in breccia Clastic
  77 Wallace sandstone Clastic
  78 Redbeds sandstone Clastic

Igneous Rocks

Igneous rocks are formed by the cooling and crystallization of hot, molten, liquid rock. If the liquid rock is above Earth's surface, it is called lava and cools to form extrusive igneous rocks. If the liquid rock is below Earth's surface, it is called magma and cools to form intrusive igneous rocks.

Picture Rock Number Rock Name Rock Formation
Keweenwan basalt
8 Keweenawan basalt Extrusive
Carbonated basalt with quartz veins
14 Carbonated basalt with quartz veins Extrusive
Larvikite
16 Larvikite  Intrusive 
Aphyric syenite dike
17 Altered pyroxenite with aphyric syenite dikes  Intrusive
Matachewan porphry
18 Matachewan Porphyry or Granite DC Intrusive
Anorthosite
37 Anorthosite Intrusive 
Sodalite syenite
41 Sodalite syenite Intrusive
Nepheline syenite
43 Nepheline syenite Intrusive
Rose quartz
46 Rose Quartz Intrusive
Chalcopyrite
47 Chalcopyrite Intrusive 
Granite
54 Granite Intrusive 
Labradorite
56 Labradorite Intrusive
Columnar dacite
57 Columnar dacite showing flow banding Extrusive
Columnar basalt
58 Columnar basalt with periodite xenoliths  Extrusive
Lepidolite
61 Lepidolite Intrusive
Porphyritic biotite granite
64 Porphyritic biotite granite Intrusive
Periditite inclusion in serpentinite
67 Peridotite surrounded by an alteration zone of serpentinite  Intrusive 
  69 Garnet-rich gabbroic anorthosite  Intrusive
  72 St.Georges red granite Intrusive
  74 Serpentinized mantle peridotite Intrusive
  75 North Mountain basalt columns  Extrusive

Metamorphic Rocks 

Metamorphic rocks form by transforming a pre-existing rock, called a protolith (proto- means first, and -lith means rock), by adding heat and pressure to it. When the protolith experiences high temperatures and pressures, the minerals that made up the protolith undergo physical and chemical changes, which create completely new minerals. These new minerals that form will eventually cool and create a completely new rock. Think of it like a caterpillar entering its cocoon, and after some time, it emerges as a butterfly!

Depending on where metamorphism is occurring, the rocks experience different levels of heat and pressure, described as the metamorphic grade. The rocks can be low, medium, or high-grade metamorphic rocks. The higher the metamorphic grade, the higher the temperature and amount of pressure the rocks were exposed to!

Metamorphic rocks can also be described based on the internal structures of the rock. In some cases, as the rock experiences pressure, the minerals that make up the rock get squashed and can be re-oriented within the rock. This can make the minerals align in the same direction and form "bands" or "stripes" of minerals, and it is called a foliated metamorphic rock. In other cases, the minerals that make up the rock do not experience the same amounts of pressure, and the minerals do not get squashed. In this case, "bands" or "stripes" are not present in the rock, and the rock is called a non-foliated metamorphic rock.

Picture Rock Number Rock Name Metamorphic Grade Foliation
Lorrain quartzite
2 Lorrain quartzite Medium to high grade Non-foliated
Green lorrain quartzite
3 Green Lorrain quartzite Medium to high grade Non-foliated
Gneiss
10 Gneiss High grade Foliated
Granite gneiss boulder
11 Granite gneiss boulder High grade Foliated
Micaeous quartzite
12 Muscovite-rich quartzite Medium to high grade Non-foliated
Quartz carbonate fuchsite serpentinite
13 Quartz Carbonate Fuchsite Serpentinite Medium grade Non-foliated
Carbonated Mafic and Felsic Igneous Rocks with Green chrome Mica Quartz veins and Pyrite
15

Carbonated Mafic and Felsic Igneous Rocks with Green chrome Mica Quartz veins and Pyrite 

Low to medium grade Non-foliated
Glacial striae
32 Glacial striae (scratches) on Lorrain quartzite Medium to high grade Non-foliated
Clacite garnet pryoxene skarn
33 Calcite garnet pyrite pyroxene skarn Low grade Non-foliated
Magenite skarn
34 Magnetite skarn Low grade Non-foliated
Epidote garnet skarn
36 Epidote garnet skarn Low grade Non-foliated
shattercones
40 Shatter cone shock structures Sudbury Impact Crater (astrobleme)

Very high grade

(specifically, impact metamorphism)

Non-foliated
Flake graphite in gneiss
42 Flake graphite in gneiss High grade Foliated
folded marble
44 Folded marble Low to high grade Non-foliated
Serpentine marble
45 Serpentine marble Low to high grade Non-foliated
Purple lorrain quartzite
53 Purple (iron-rich) Lorrain quartzite Medium to high grade Non-foliated
50th anniversary gneiss
59 50th Anniversary Gneiss  High grade  Foliated
slate
60 Slate Low grade Foliated
metabasalt
62 Metabasalt Low grade Non-foliated
Nephrite jade
65 Nephrite Jade  High grade Non-foliated
Serpentinite
66 Serpentinite Low grade Foliated
Oldest rock on Earth
71 Oldest Rock in the World - tonalitic gneiss High grade Foliated

Ores

Ore is a type of rock that is made of a combination of minerals that contain metals or elements that are important for making materials used in our everyday lives. Ore is the raw product that is extracted from mining operations. It is then processed to separate the valuable minerals from the invaluable minerals, which are then sold to make a profit. 

Picture Rock Number Rock Name
Gold ore
19 Gold ore
Cobalt-nickel vein
23 Cobalt-Nickle Vein
Nickel-cooper ore
48 Nickle-copper ore
Sediment-hosted zinc-lead ore
73 Sediment-hosted zinc-lead ore
  79 Lead-zinc ore
  80 Massive sulphide ore

Fossils

Fossils are the preserved remains, or traces of remains, of ancient species. Fossils are not the remains of the organism itself, but are rocks! 

Picture Rock Number Rock Name
  76 Petrified Wood