Calcite                                    Mineral Group: CARBONATES
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Calcite
  • Calcite is a very common mineral. It is found in most places on earth. It is a sedimentary mineral.
  • Calcite crystals come in many different shapes.
  • There are more than 300 different crystal shapes. This is more than any other mineral.
  • People who decide to collect only calcite can have a very interesting collection because there are so many shapes that calcite comes in.
  • One common use for calcite is that it is used in making cement.

Scalenohedral Calcite Crystals w/ green coating (chlorite?)
Mathers Quarry, Saint-Eustache, Quebec  CANADA

 

Calcite with Barrerite coating
Cantung Mine, Tungsten, Northwest Territories    CANADA

 
Calcite Crystals
  • These photos are of calcite found  by T. Elliott in the LaFarge Quarry, Dundas, Ontario, CANADA

Dog-Tooth Calcite Crystals
LaFarge Quarry, Dundas, Ontario, CANADA
Dog-Tooth Calcite Crystals
  • this crystal shape is called dog-tooth because they look like the canine teeth
     

Lockport Quarry, New York, USA

SPECIMEN: Dog-Tooth Calcite Crystals with Sphalerite
SPECIMEN ORIGIN: LaFarge Quarry, Dundas, Ontario, CANADA

SPECIMEN: Dog-Tooth Calcite Crystals
SPECIMEN ORIGIN: LaFarge Quarry, Dundas, Ontario, CANADA

SPECIMEN: Dog-Tooth Calcite Crystals
SPECIMEN ORIGIN: LaFarge Quarry, Dundas, Ontario, CANADA
Calcite
  • Other minerals like dolomite are often found with calcite crystals.
  • Calcite is often found in vugs and in veins in sedimentary rocks.

     

     


SPECIMEN: Pink Dolomite and Dog-Tooth Calcite Crystals
SPECIMEN ORIGIN: LaFarge Quarry, Dundas, Ontario, CANADA

SPECIMEN ORIGIN: BRAZIL
Calcite Cemented Limestone Breccia
SPECIMEN ORIGIN: LaFarge Quarry, Dundas, Ontario, CANADA

SPECIMEN ORIGIN: LaFarge Quarry, Dundas, Ontario, CANADA

SPECIMEN ORIGIN: LaFarge Quarry, Dundas, Ontario, CANADA
Honey Brown Calcite with Quartz Crystals
  • Calcite crystals can also be rhombohedrons (6 sided).

SPECIMEN ORIGIN: Rockwood, Michigan, USA
Calcite Rhomb
  • This calcite specimen still looks like a rhomb (squished box) but its edges are rounded.
  • Its surface is also like satin and looks pearly.
  • Calcite breaks into rhombs very easily, especially when exposed to the weather.
  • This piece has been tumbled with other pieces of calcite as it tumbled down the mountain side.
  • it is also fluorescent
  • perfect cleavage
  • smooth flat breaks
  • white streak

SPECIMEN: CALCITE Rhomb
SPECIMEN ORIGIN: North Bay, Ontario, CANADA
Weathered Calcite
  • This piece of pink calcite was buried under a thick layer of forest soil.
  • As the water moved along the rock, it eroded it.
  • That is why the calcite is criss-crossed with fine sharp lines and is a darker color.
  • The part of the calcite that was freshly broken or cut, is still a fresh pink color.

SPECIMEN: Weathered Calcite surrounding HORNBLENDE crystals
SPECIMEN ORIGIN: Eganville, Ontario, CANADA
Pink Calcite
  • This picture shows a massive piece of pink calcite that has been freshly broken. Notice how shiny the surface is and how pink the color is. This specimen is from the same location as the weathered piece above.

SPECIMEN: Pink Calcite
SPECIMEN ORIGIN: Eganville, Ontario, CANADA
Blue Calcite
SPECIMEN ORIGIN: Gouveneur Talc#4 Quarry, Gouverneur, New York, USA
Dog-Tooth Calcite and Dolomite

 

SPECIMEN ORIGIN: Walker Brothers Quarry, Thorold, Lincoln County, Ontario, CANADA

calcite crystal  Picher, Oklahoma USA

Calcite on Aragonite  HUNGARY
We are still trying to identify the exact location this specimen came from. This is what happens when you label something on a napkin, in a foreign language & then leave it outside for the mice to discover over the winter!;)
Calcite  from Lincoln Quarry, Beamsville, Ontario  CANADA
Calcite  from Lafarge Quarry,  Dundas, Ontario  CANADA
Calcite - Cauliflower Calcite (fluorescent)  from Grand River, Paris, Ontario  CANADA
Calcite  from Sweetwater Mine, The Lead Pillar Room 1,300 ft. level, Doe Run Mine, ASARCO Inc., Reynolds County, Missouri  USA
Calcite - Honey Brown Calcite Cubes   from Sora Limestone Quarry, Rockwood, Michigan  USA
Calcite  from Aguathuna, Newfoundland  CANADA

Calcite and its kin
© Bert Ellison 1999 - 2002

The formula for calcium carbonate is simple enough – CaCO3 – but the mineral itself appears in a bewildering variety. Hiding behind its hexagonal ditrigonal scalenohedral class (whew!) are over 300 forms and more than 1000 combinations. Little wonder that some of our collections are tough to identify without other tests (See "Field Tests" in a recent newsletter.)

We all know that calcite stands for number 3 on Mohs scale between gypsum and fluorite, that it’s easily scratched with the knife, that it fizzes readily in dilute acid. It’s also kissin’ cousin to aragonite which forms the shells of many clams and brachiopods. Calcite has more forms and habits than any other mineral and add to that a wide spectrum of colors from clear to black. But the streak is always white or a pale color.

A variety called Iceland spar is strongly doubly refractive which means that a clear cleavage piece, when laid on a mark on paper will display two separate images. This property was put to good use in pre-Polaroid days in polarizing microscopes – Nicols prisms. A suitably pure piece was sliced in a special way, one piece mounted in the tube and the other under the rotating stage. Thin sections of rock when placed on the stage displayed useful colors and shapes.

The different varieties of calcite may be grouped like this: ordinary calcite; limestones, marbles, chalk and marl, and spring, stream and cave deposits. These groups deserve fuller discussion but for now the notes will be limited to one or two.

This mineral is the basis of limestone, itself of many kinds. Worldwide, most limestone is marine in origin – laid down in warm shallow waters. While fossils play quite a role in many deposits, drawing calcium carbonate out of seawater, much limestone just precipitates out. This is because cold seawater – any water – holds vast amounts of this compound in solution. But if this water warms up in shallow basins like the Persian Gulf (or our teakettles!), the mineral comes out as very fine grains and crystals; this may be the start of chalk. Even fish disturbing such saturated areas may leave a milky trail of precipitating calcite.

A famous example of this fine "lithographic" limestone (yes it once was used to make printing blocks) is in Solenhofen, Germany. It’s so fine grained that the imprints of even leaves and insects are preserved in exquisite detail. We’ve all heard about Archaeopteryx, the earliest (Jurassic) bird.

A famous limestone comes from the Ordovician (age) near Winnipeg. This Tyndall rock is used throughout our parliament buildings and hundreds elsewhere. The mottling is considered to be dolomitized feeding trails of animals.

Under suitable conditions calcite transforms to marble, either sugary or very fine in texture. Its use ranges from underfoot as chips in terrazzo to the glories of Michelangelo’s "David" in Florence. And why not? Nearby are the 200 quarries of famous Carrara marble. After 200 years over a million tonnes a year are still produced, mostly for buildings.

During WW2, to curry favor with Hitler, Mussolini presented him a birthday gift for his "Eagle’s Nest" at Berchtesgarden – a huge slab of red marble for the lintel of the fireplace. Ugly, its only virtue was its richness in ammonite (Jurassic?) fossils. Hitler hated it!

 

 

 

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