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& Minerals Information
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50 pages of this Stones & Minerals Information section are
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Source: Mineral Galleries
Chemistry: CaCO3, Calcium Carbonate
Uses: In cements and mortars, production of lime, limestone
is used in the steel industry; glass industry, ornamental stone,
chemical and optical uses and as mineral specimens.
Calcite's Physical Properties Specimens
Calcite, which gets its name from "chalix" the Greek
word for lime, is a most amazing and yet, most common mineral.
It is one of the most common minerals on the face of the Earth,
comprising about 4% by weight of the Earth's crust and is formed
in many different geological environments. Calcite can form
rocks of considerable mass and constitutes a significant part
of all three major rock classification types. It forms oolitic,
fossiliferous and massive limestones in sedimentary environments
and even serves as the cements for many sandstones and shales.
Limestone becomes marble from the heat and pressure of metamorphic
events. Calcite is even a major component in the igneous rock
called carbonatite and forms the major portion of many hydrothermal
veins. Some of these rock types are composed of better than
99% calcite. Why would a collector be interested in such a common
mineral? Its extraordinary diversity and beauty!
With calcite so abundant and so widely
distributed it is no wonder that it can be so varied. The crystals
of calcite can form literally a thousand different shapes by
combining the basic forms of the positive rhombohedron, negative
rhombohedron, steeply, moderately and slightly inclined rhombohedrons,
various scalahedrons, prism and pinacoid to name a few of the
more common forms. There are more than 300 crystal forms identified
in calcite and these forms can combine to produce the thousand
different crystal variations. Calcite also produces many twin
varieties that are favorites among twin collectors. There are
also phantoms, included crystals, color varieties, pseudomorphs
and unique associations. There simply is no end to the varieties
There are several varieties of calcite
and it would be impossible to describe them all. However there
are a few standouts. Possibly the most well-known of calcite's
varieties is its most common form, the classic scalenohedron
or "Dogtooth Spar" as it is sometimes called. This
variety appears as a double pyramid or dipyramid, but is actually
a distinctly different form. The point of the scalenohedron
is sharp and resembles the canine tooth of a dog, hence the
name. Beautiful clear colorless or amber-orange examples of
this variety are considered classics and outstanding examples
come from Pugh Quarry, Ohio; Cornwall, England and Elmwood,
Tennessee but the variety is found worldwide.
Not necessarily a variety of calcite,
cave formations are certainly a unique aspect of calcite's story.
Calcite is the primary mineral component in cave formations.
Stalactites and stalagmites, cave veils, cave pearls, "soda
straws" and the many other different cave formations that
millions of visitors to underground caverns enjoy are made of
calcite. It is the fact that calcite is readily dissolved
that these formations occur. Overlying limestones or marbles
are dissolved away by years and years of slightly acidic ground
water to percolate into the caverns below. In fact the caverns
themselves may have been the result of water dissolving away
the calcite rich rock. As the calcite enriched water enters
a relatively dry cavern, the water starts to evaporate and thus
precipitate the calcite. The resulting accumulations of calcite
are generally extremely pure and are colored if at all, by very
small amounts of iron or other impurities.
Mexican onyx is a variety of calcite
that is used extensively for ornamental purposes. It is carved
into figurines and is so popular that almost every child in
the USA owns a small onyx animal or two. Carvings such as vases,
bookends, plates, eggs, obelisks, pyramids and statues are all
popular. It is not the same onyx as the quartz variety of onyx
which is a little more precious (it is used in jewelry) and
is banded white and black. To avoid confusion it is best to
refer to it as Mexican Onyx. Mexican onyx is banded with multiple
orange, yellow, red, tan, brown and white colors that have marble-like
texture. The carvings are quite attractive and affordable; a
Another variety is the so called
"Iceland Spar", which is basically clear cleaved fragments
of completely colorless (ice-like) calcite. Originally discovered
and named after Eskifjord, Iceland where the calcite is found
in basalt cavities. In rock shops around the world, Iceland
spar is available in large quantities and at affordable prices
and are popular among children. Most of today's Iceland spar
comes from Mexico. The Iceland spar displays the classic cleavage
form of calcite, the rhombohedron. Iceland spar was and is used
for optical equipment and during World War II it was a strategic
mineral as it was used for the sighting equipment of bombardiers
and gunners. It is Iceland spar that best demonstrates the unique
property of calcite called double refraction.
Double refraction occurs when a ray
of light enters the crystal and due to calcite's unique optical
properties, the ray is split into fast and slow beams. As these
two beams exit the crystal they are bent into two different
angles (known as angles of refraction) because the angle is
affected by the speed of the beams. A person viewing into the
crystal will see two images ... of everything. The best way
to view the double refraction is by placing the crystal on a
straight line or printed word (the result will be two lines
or two words). There is only one direction that the beams are
both the same speed and that is parallel to the C-axis or primary
trigonal axis. Rotation of the crystal will reveal the direction
in the crystal that is parallel to the C-axis when the line
or word becomes whole again. By contrast, the direction perpendicular
to the C-axis will have the greatest separation. The extremely
high index of refraction of calcite that causes the easily seen
double refraction is also responsible for the interference colors
(pastel rainbow colors) that are seen in calcites that have
Fluorescence, phosphorescence, thermoluminescence
and triboluminescence are other important properties of calcite.
Although not all specimens demonstrate these properties, some
do quite well and this is diagnostic in some cases. One notable
case of fluorescence occurs at Franklin, New Jersey where the
massive calcite is enriched in a small amount of manganese and
fluoresces a bright red under UV light. Some Mexican Iceland
spar can fluoresce a nice purple or blue color and unique specimens
will even phosphoresce (continue to glow) after the UV source
has been removed. Triboluminescence is supposedly a property
that should occur in most specimens, but is not easily demonstrated.
It occurs when the specimen is struck or put under pressure;
in a dark room the specimen should glow when this happens.
The best property of calcite is
the acid test. Why? Because calcite always will effervesce (bubble)
when even cold weak acids are placed on specimens. Even the
cement in sandstones will effervesce assuring the geologist
of identification of the cementing mineral.
The carbon dioxide gas (CO2) is
given off as bubbles and the calcium dissolves in the residual
water. Any acid, just about, can produce these results, but
dilute hydrochloric acid or vinegar are the two recommended
acids for this test. Other carbonates such as dolomite or siderite
do not react as easily with these acids as does calcite and
this leads to differentiating these somewhat similar minerals
Calcite is intricately tied to carbon
dioxide in another way. Since many sea organisms such as corals,
algae and diatoms make their shells out of calcite, they pull
carbon dioxide from the sea water to accomplish this in a near
reverse of the reaction above. This is fortuitous for us, as
carbon dioxide has been found to be a greenhouse gas and contributes
to the so called "greenhouse gas effect". Environmentally
then, calcite is very important and may have been quite important
to the successful development of our planet in the past. By
pulling carbon dioxide out of the sea water, this biological
activity allows more of the carbon dioxide in the air to dissolve
in the sea water and thus acts as a carbon dioxide filter for
the planet. Environmentalists are now actively engaged in determining
if this activity can be increase by human intervention to the
point of warding off the "greenhouse gas effect".
A significant amount of calcite precipitation in sea water is
undoubtedly inorganic, but the exact amount that this contributes
is not well known. Calcite and other carbonate minerals are
very important minerals in the ocean ecosystems of the world.
Calcite is not the only calcium
carbonate mineral. There are
no less than three minerals or phases of CaCO3. Aragonite and
vaterite are polymorphs (latin for "many shapes")
with calcite, meaning they all have the same chemistry, but
different crystal structures and symmetries. Aragonite is orthorhombic,
vaterite is hexagonal and calcite is trigonal. Aragonite is
a common mineral, but is vastly out distanced by calcite which
is the more stable mineral at most temperatures and pressures
and in most environments. Vaterite on the other hand is extremely
scarce and rarely seen. Aragonite will over time convert to
calcite and calcite pseudomorphs after aragonite are not uncommon.
Calcite is truly one of the best
collection type minerals. There are lots of interesting forms
and varieties as well as colorful and beautiful specimens to
collect. It is generally easy to identify using its rhomohedral
cleavage, reaction to acid and double refraction and makes for
a great classroom example of these properties. If it is not
the significant mineral on a specimen, it might be an accessory
to other wonderful minerals and only enhancing their attractiveness.
With its many different forms, environments, associations and
colors, a collector could never have all possible combinations
of calcite covered.
PHYSICAL CHARACTERISTICS OF CALCITE:
Color is extremely variable but generally white or colorless
or with light shades of yellow,orange,
blue, pink, red, brown, green, black and gray. Occasionally
Luster is vitreous to resinous to
dull in massive forms.
Transparency: Crystals are transparent
Crystal System is trigonal; bar 3
Crystal Habits are extremely variable with almost any trigonal
form possible. Common among calcite crystals are the scalenohedron,
rhombohedron, hexagonal prism, and pinacoid.
Combinations of these and over three hundred other forms can
make a multitude of crystal shapes, but always trigonal or pseudo-hexagonal.
Twinning is often seen and results in crystals with blocky chevrons,
right angled prisms, heart shapes or dipyramidal shapes. A notch
in the middle of a doubly terminated scalenohedron is a sure
sign of a twinned crystal. lamellar twinning also seen resulting
in striated cleavage surfaces. Pseudomorphs after many minerals
are known, but easily identified as calcite. Also massive, fibrous,
concretionary, stalactitic, nodular, oolitic, stellate, dendritic,
granular, layered, etc. etc.
Cleavage is perfect in three directions,
Fracture is conchoidal.
Hardness is 3 (only on the basal pinacoidal faces, calcite has
a hardness of less than 2.5 and can be scratched by a fingernail).
Specific Gravity is approximately 2.7 (average)
Streak is white.
Other Characteristics: refractive indices of 1.49 and 1.66 causing
a significant double refraction effect (when a clear crystal
is placed on a single line, two lines can then be observed),
effervesces easily with dilute acids and may be fluorescent,
phosphorescent, thermoluminescence and triboluminescent.
Associated Minerals are numerous
but include these classic associations: Fluorite, quartz, barite,
sphalerite, galena, celestite, sulfur, gold, copper, emerald,
apatite, biotite, zeolites, several metal sulfides, other carbonates
and borates and many other minerals.
Notable Occurrences include Pugh
Quarry, Ohio; Rosiclare, Illinois; Franklin, New Jersey; Elmwood,
Tennessee; Brush Creek and other Missouri, Wisconsin, Kansas
and Oklahoma localities, USA; Andreasburg, Harz Mountains and
Saxony, Germany; Brazil; Guanajuato, Mexico; Cornwall, Durham
and Lancashire, England; Bombay area of India; Eskifjord, Iceland;
many African localities as well as others around the world with
their own unique varieties. Best Field Indicators are crystal
habit, reaction to acid, abundance, hardness, double refraction
and especially cleavage.
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The energy properties of Calcite
are interesting to me. I don't know how many of you have noticed
how energy flows in various stones but I like watching it so
I have. In calcite - it's kind of like a dotted line of energy
flow instead of a straight line energy flow. There are slight
gaps in the flow, I guess is a better way to describe it. For
me, this makes it perfect for the physical vibrational range
when it comes to healing.
I've used calcite for feet and to
augment massage. If you have tired feet, get yourself a calcite
ball and roll the ball of your feet on it with a slight pressure.
It works WONDERS for your energy flow. We store a lot of stress
in our feet and energy can get trapped there. Using a calcite
wand in the small of your back is also good for joint pain in
that area. Calcite is great for re-establishing the flow of
energy in bones and joints and helping to regenerate bone growth.
Now, it doesn't do it by itself. You have to focus and work
with it, but it does work well. If you're healing a broken bone,
use calcite to build up the energy flow. Shoulder and neck pain...
well there are other stones for that but, under the blade of
the shoulders, calcite is great!
mental capacity. Used by those who wish to try astral projection.
Cunningham: Folk name: Iceland Spar Powers: Spirituality, Centering,
Peace, Love, Healing, Purification, Money, Protection, Energy.
Uses: Calcite, a transparent crystal, is found in a wide variety
of colors, including clear, green, pink, orange, and blue. It
has the unique optical quality of double refraction. Draw a
line with a pen on a piece of paper, then place a piece of calcite
over the line. When you look through the stone, the line will
appear to be doubled. This property causes calcite to be used
in spells to 'double the power' of the rite. It is placed on
the altar or worn during magical rituals for this purpose.
Calcite: Receptive, Moon, Water This stone is utilized in
spirituality rituals. It is perfect as a focus of contemplation
Pink Calcite: Receptive, Venus, Water Held in the hand,
it is calming, centering, and grounding. It is also used in
Calcite: Receptive, Venus, Water A healing stone when worn
on the body, or placed between flaming purple or blue candles.
During purification ceremonies wear or use it.
Calcite: Receptive, Venus, Earth This stone draws money
and prosperity to the household, especially when surrounded
by flaming green candles every morning for a few minutes.
Calcite: Projective, Sun, Fire A protective stone and lends
energy to the body when held.
Copyright: Cinnamon Moon & River WildFire Moon (Founders.)
All rights reserved.
constructed by Dragonfly