Types of Rocks In Lake Ontario: 5 Common Collectible Rocks and Fossils You Can Find

Lake Ontario is the 13th largest lake in the world and the smallest of the Great Lakes.

If you include its islands, it has a shoreline of 712 miles (1,146 km) long.

That equates to a lot of opportunities to find rocks on its shoreline.

Types of Rocks In Lake Ontario

You can find the following 5 rocks at Lake Ontario:

Clastic Sedimentary Rocks

The majority of people think about sedimentary rocks when they think of clastic sedimentary rocks.

Clastic sedimentary rocks contain pre-existing rock fragments (clasts).

Weathering loosens rock fragments, which are subsequently moved to a depression or basin where sediment is trapped.

Sedimentary rock is formed when sediment is submerged deeply and crushed and cemented.

These sedimentary rocks can contain particles as small as tiny clay to as large as massive boulders.

Their names are derived from the size of their clasts, or grains.

Clay is the smallest particle, followed by silt, and finally sand.

Pebbles are grains with a diameter of more than 2 millimeters.

Shale is primarily composed of clay, siltstone is composed of minuscule silt-sized grains, sandstone is composed of tiny sand-sized clasts, but conglomerate is composed of pebbles encased in a sand or mud matrix.


All limestone types are sedimentary rock made mostly of calcite (calcium carbonate) or calcium-magnesium double carbonate (dolomite).

Tiny fossils, shell pieces, and other fossilized detritus are often found in it.

On careful observation of the rock surface, these fossils are often apparent to the unassisted eye, although that isn’t always the case.

Gastropod fossils are common around Lake Ontario.

The grain of certain limestone kinds is exceedingly fine.

Limestone is a form of sedimentary rock that is rather abundant.

It is largely made up of the minerals aragonite and calcite, both of which are crystal types of calcium carbonate.

Limestone is formed when these elements precipitate out of dissolved calcium-containing water.

This may happen via both nonbiological and biological mechanisms. However, biological processes are preferred.

Limestone is unevolved marble.

Non-geologists may find the categorization of marbles and limestones to be perplexing.

The same stone might be sold as limestone one time and then as marble another time and location.

The intricacies that distinguish grades and kinds of stones are often beyond the interest and skill of the average person.

Basically, marble is formed by the application of heat and pressure to limestone.

Igneous Granite

The term “granite” is derived from the Latin word granum, which means “grain,” and refers to the coarse-grained texture of such a fully crystalline rock.

Granite is a lightly-colored lava rock (igneous rock) with big granules that can be seen without a magnifying glass.

It is formed by the gradual crystallization of magma under the surface of the Earth. 

Granite is mostly quartz and feldspar, with some amphiboles, mica, and other minerals thrown in for good measure.

Granite has a red, gray, pink, or white appearance, with black mineral grains evident throughout the rock, due to its mineral makeup.

Many people are familiar with granite since it is the most prevalent igneous rock found on the planet and because it is used to produce a variety of everyday products.

Countertops, paving stone, floor tiles, curbing, building veneer, stair treads, and cemetery monuments are examples of these materials.

Granite is employed in almost every aspect of our lives, particularly if we reside in a major contemporary metropolis.


Gneiss is a high-grade metamorphic rock, which means it has undergone more heat and pressure than schist.

It is generated when granite, or sedimentary rock, undergoes a metamorphosis.

Gneiss has remarkable foliation, which is made up of alternating layers of various minerals.

Unlike schist and slate, however, gneiss doesn’t really fracture along foliation planes because only about half of the minerals generated during metamorphism are oriented in thin layers.

The strata are frequently sub-parallel, i.e. they will not have a consistent thickness, and are discontinuous due to the crudeness of the foliation.

Gneiss is a coarse metamorphic rock with structural banding also known as gneissic banding, but underdeveloped schistosity and unclear cleavage in traditional North American and English use.

Gneiss is often linked to big mountain-forming events.

Felsic or Sedimentary igneous rocks are exposed to extreme pressures and temperatures during these periods, which are caused by the depth of burial, closeness to volcanic intrusions, and tectonic forces.

The earliest crustal rocks known are gneisses from western Greenland. Gneiss is a word from the Middle Ages that means “bright” or “sparkling.”


Jasper, flint, and chert, are terms often used by the public and geologists to describe opaque microcrystalline quartz specimens.

A single hand specimen may be referred to as “chert” by one individual, “jasper” by another, and “flint” by a third.

The word “jasper” is more like a gemological title than a material designation used by geologists.

People who pick superb bits of transparent microcrystalline quartz to make cabochons, tumbling stones, spheres, or other lapidary-related projects are most likely to use the term “jasper”

Jasper is an opaque, impure type of silica that is generally red, yellow, brown, or green in color, and occasionally blue.

It is an aggregation of chalcedony and/or microgranular quartz and other mineral phases.

Iron inclusions provide the prevalent red color.

Jasper has a smooth finish and is often used as an adornment or a gemstone.

It is ground and polished and it is used to make items such as seals, vases, and snuff boxes. Jasper’s specific gravity ranges from 2.5 and 2.9.

Heliotrope (meaning sun-turn, commonly known as bloodstone) is a green variation with crimson dots that is one of the customary birthstones for March.

Jaspillite is a different banded-iron-formation rock with characteristic jasper bands.

Lake Ontario provides the intrepid rockhound with the basic rocks that they need to make any day something to remember.

Not only is the diversity of rocks at the lake great, but the rocks are all perfectly polished and rounded by centuries of polishing by the movement of the waves.

Get your rocks before there is only sand left.

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Types of Rocks In Lake Ontario