FreeShip- Marble, Granulated, Calcium Carbonate, Calcite- (Prompt rebate on orders with 3 or more FreeShip items!)

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Fine white marble is a seductive material. The reason for that might be found in a scientific fact. Although this is not massive marble, but fine marble grains, you can still see the sparkle of calcite crystals when you look at it. When massive, light is split into 2 rays by the "birefringence" of calcite crystals and in massive form it can travel to a depth of 17 mm or more, bouncing around inside the marble until it is finally refracted back to us as a beguiling glow which brings a luster to marble sculptures of any kind, which is why many sculptors prefer to work in white (calcite) marble and many builders have used marble to construct monuments and great buildings. The architectural use of marble is centuries and millennia old.

Since this white calcite marble is in a granulated form, consisting of particles from about 0.1 mm to 0.7 mm (with some pieces outside that range to 1+ mm and 0.02 mm), not all of the following information will apply as much, but quite a bit of it does apply. Granulated calcite marble is a pure calcium carbonate. But calcium carbonate refers only to a chemical compound, CaCO3. It says nothing about the crystal structure of minerals that are CaCO3. There are 3 types of such minerals: calcite, aragonite, and vaterite. The crystalline structure of those three forms of CaCO3 are different and some of their physical properties differ. Calcium carbonate has several uses. One which is used in the arts is as a filler for resins and cementitious mixtures (such as white portland cement concrete or mortar). It could also be used experimentally as a white gypsum cement filler. Usually calcium carbonate is only available in a powdered form.

I am cheating by duplicating a description of rounded marble stones to supply facts about white calcite marble in general. Marble powder or granules are in a different class of fillers than other common ones like silicates. Many inexpensive fillers you will commonly use are siliceous, being silica (an oxide of silicon, silicon dioxide), or mixtures of silicates and other oxides. Common sand used by the dump truck load is mostly silica. Those fillers will be much harder materials with mohs hardnesses of up to 7. Forms of calcium carbonate like marble or limestone are softer with mohs hardnesses of around 3. Other softer fillers are dolomite and aragonite with mohs hardnesses of 3.5 to 4. Talc is the softest filler with a moh's hardness of 1.

This is a quote about a particular use from a visitor to the 9/11 memorial of the NYC Trade Center buildings { https://usenaturalstone.org/mad-marble-geological-look-classic-stone/ } :
"Despite the emergence of marble lookalikes, there’s nothing quite like the real thing. Real marble has qualities that cannot be replicated in a lab. I recently visited the 9/11 Memorial, a sobering space of monument, museum, and reflection. Next to the footprint of the fallen towers, rises the one part of the site that inspires optimism. Called the Oculus, it is part transit center, part shopping mall, and its soaring white ribs beckon investigation.
Visitors who step inside are rewarded with a vast, cathedral-like space, covered in pure white marble. The combination of natural light, natural stone, and creative architecture transform the somber mood into a hopeful one. Wandering around the expansive structure, I finally put my finger on my favorite quality of real marble. Light penetrates into the white stone, then radiates back out in heavenly luminosity, filling the room with a warm, soft glow. Leave it to a stone like marble to completely alter the mood of a building. Marble has been a metaphor for worship, reverence, and beauty for millennia. Its ability to do that is all the more appreciated today."
For the metaphysically minded, marble is a grounding stone. It embodies security, strength and stability. White marble is also used as a cleansing stone, often used in the fields of naturopathy and homeopathy for its balancing qualities. Continuing in the metaphysical tract, what are the properties of a calcite crystal, which marble has in abundance? Calcite has the ability to amplify and cleanse energy, as well as clear and balance the chakras (for those not so metaphysically inclined you can find info on the 7 Chakras here: { https://www.healthline.com/health/what-are-chakras }. It can also absorb and transform negative energy. Calcite is a crystal that calms the mind and enhances mental clarity, and it also connects the emotions with the intellect.

Calcite based marble is most abundant (dolomite based is less so). Marble is a metamorphic rock (that has been changed by great heat and pressure) composed of recrystallized carbonate minerals. The refractive index (RI) of marble is relatively low among rocks and minerals. The mineralogy of marble allows light to penetrate into the rock which brings a lifelike luster to marble sculpture.
The snowy-white Carrara marble is a famous type of marble from the Italian town of Carrara, in northern Tuscany. It is especially pure and translucent. Renaissance artists like Michelangelo and Antonio Canova favoured it for sculptures and many modern sculptors prefer it. One of the most famous sculptures using Carrara marble is perhaps "David", a masterpiece created by Michelangelo in 1504. The statue became one of the most celebrated and recognized works of Renaissance sculpture, a symbol of strength and beauty. The word marble is derived from a Greek work “marmaros”, meaning shining stone. It was highly prized by Roman and Greek architects and artists because it was considered a high status symbol of cultural tradition and sophistication.

The science behind materials which have beauty is quite interesting and adds another dimension of appreciation for such materials. Artists who are familiar with that science, and have a greater appreciation for their materials often create greater art. Understanding science takes time, requiring study. In the arts, when creativity is at its peak, artists may have 10 ideas in their heads wanting to be expressed in their next creations, which will consume the majority of their time. For scientists who spend most of their time studying science, a detour appreciating a thing's beauty is not as expensive (in time). Appreciation of the beauty of spirals in a sunflower's seeds is faster than studying the mathematics of such spirals (which is the "golden spiral", a logarithmic spiral, and which has the growth factor of the "golden ratio", exhibited by the ratio of the ancient greek building called the Parthenon, designed by Greek mathematician and sculptor Phidias, which no doubt originally included marble for part of its beauty).

As mentioned, most marble is calcite based. Calcite has 3 perfect cleavage planes and optically pure calcite has three different crystal axes perpendicular to its cleavage planes (calcite is one of the most difficult of all minerals to be cut because of perfect cleavage in 3 directions). Calcite's optical properties are not the same in all directions. That is key to why the following description is true:
The Refractive Index (RI) of calcite is 1.49 and 1.64-1.66, a triple value (but in effect a double value), meaning its 3 crystal axes inhibit the speed of light broadly into 2 speed differences (the speed of light is usually given as it is in a vacuum (because the vacuum in outer space is where its velocity is highest). When light passes through one medium (such as air) and into another denser medium (such as diamond) it is bent and slowed at that point. A denser medium as a rule has a higher Refractive Index and slows down the speed of light more. Light travels with a higher velocity through a crystal axis that has the smallest refractive index and this axis is called the fast axis. An axis which has the highest refractive index is called a slow axis since the velocity of light is the lowest through this axis.

Uniaxial crystals are optically transparent crystals in which the refractive index of one crystal axis is different from the other two crystal axes (which usually have close refractive indices). The unique axis is called the "optic axis". The optic axis can be the fast or the slow axis for the crystal depending upon the material. Materials such as calcite and ruby have the fast axis as the optic axis. They are said to be "negative uniaxial" crystals. Materials such as quartz and rutile have the slow axis as the optic axis. They are "positive uniaxial" crystals. Both types of uniaxial crystals display "birefringence" or "double refraction".
The classic example of double refraction is when printed letters on a piece of paper covered by a clear calcite crystal show up as doubled when viewed through the calcite crystal. It is an effect of the speed of light being changed in two ways when passing through a crystal. In effect it splits a beam of light.

Double refractive or birefringent materials are used in many optical devices, such as liquid crystal displays, color filters, polarizing prisms, light modulators, and wave plates. Birefringence was first described in calcite crystals by the Danish scientist Rasmus Bartholin in 1669. Since then, many birefringent crystals have been discovered. One of note that is strongly birefringent (and that I hold in high esteem) is silicon carbide, also known in another description as "star dust", and as "moissanite" (a visual substitute for diamond which actually has a higher refractive index than diamond).
That splitting of light into 2 speeds traveling as doubled rays is what adds a boost to the luminescence of pure white calcite marble (even though marble is not composed of a single large calcite crystal but many tiny grains of calcite crystals). Light bounces around a little more in it than in non-birefringent materials.
Calcite's variation along its axes both optically and mineralogically (such as hardness, and other properties) has many practical consequences in preparing and quarrying some marbles. Because calcite's crystals are doubly refractive (transmitting light in two directions and more light in one direction), slabs prepared for uses in which translucency is significant are therefore cut parallel to that direction. The actual bending of marble slabs has been attributed to the directional thermal expansion of calcite crystals on heating.

More facts about marble of general interest (with apologies to Wikipedia and other websites for scattered general references):
The above information was concerned with calcite marble specifically. The other type of marble is dolomite marble which does not have the abundance of calcite but is still of carbonate origin. Dolomite marble is mainly composed of calcium magnesium carbonate instead of calcium carbonate (calcite). It is somewhat harder than calcite marble, is not as reactive when in contact with acids, and tends to be less common in pure white, and more common in colors such as pink, green, and gray.

Marble, being of metamorphic origin, is often found interbedded with other metamorphic rocks as mica schists, phyllites, and gneisses and are most common in the older layers of Earth’s crust that have been deeply buried in regions of extreme folding and igneous intrusion (liquid rock consisting of superheated lava).
The change from limestones rich in fossils next to true marbles in such metamorphic regions is common and can be found in marbles at deposits such as the famous Carrara, Italy marble and the Bergen, Norway marble.

Many marbles contain other minerals that are usually silicates of lime or magnesia. Diopside is very frequent and may be white or pale green; white bladed tremolite and pale-green actinolite also occur; the feldspar encountered may be a potassium variety but is more commonly a plagioclase (sodium-rich to calcium-rich) such as albite, labradorite, or anorthite. These minerals represent impurities in the original limestone, which reacted during metamorphism to form new compounds.
In some cases the original bedding of the calcareous sediments can be detected by mineral banding in the marble. The silicate minerals, if present in any considerable amount, may colour the marble; e.g., green in the case of green pyroxenes and amphiboles; brown in that of garnet and vesuvianite; and yellow in that of epidote, chondrodite, and titanite. Black and gray colours result from the presence of fine scales of graphite.

The so-called onyx marbles consist of concentric zones of calcite or aragonite deposited from cold-water solutions in caves and crevices and around the exits of springs. They are, in the strict sense, neither marble nor onyx, for true onyx is a banded chalcedony which is a form of the much harder silica (silicon dioxide).
Onyx marble was the “alabaster” of the ancients, but alabaster is now defined as gypsum, a calcium sulfate rock, quite removed from either calcite marble or dolomite marble. Alabaster as it is now recognized, is a form of pure gypsum, the finest of which will have transparent crystals which lend a high degree of translucence to the massive stone, which is softer even than marble itself which is considered soft by the sculptors who carve it.

Marble quarries exist all over the world and several locations in the US have large quarries of marble. There are quarries of white and gray marble at Alabama, Georgia, Tennessee, Yule, Colorado,and New England (specifically Vermont). It is perhaps Georgia marble and marble from Vermont which is more widely known and that qualifies as the finest US marble. Georgia marble has been used all around the world and in many historical monuments and buildings in Washington, DC, including the Lincoln Memorial, parts of the Capitol building and many museums in Washington and around the country. Quarrying has been carried our there since the 2nd half of the 19th century. In Vermont, the Danby quarry is the largest underground marble quarry in the world. The quarry is entered through the same opening that has been in use for over 100 years. From the outside of Dorset Mountain the quarry looks the same as it did a century ago. It was the first marble quarry in the US and produces marble known for it's grain fineness and purity. It is also the finest marble in the world if you consider density and durability to be the yardstick. Marble is a beautiful stone but as building stone goes it is far softer than its rival, granite. Marble can take a stain (granite will not) depending on how dense the grains are. The absorption rate of marble is a reflection of how dense the stone is. Denser marble doesn't stain as easily. Vermont marble's absorption rate is between 0.06% and 0.08%. Fine and famous Carrara marble has an absorption rate of 0.13%, almost twice as much. Other well known marbles have rates higher than that, 0.15% to 0.18%. So, because of it's density Vermont marble is famous in circles that deal in natural stone slabs as they are used in expensive kitchens and other parts of expensive homes. It is so much in demand that shortages have existed from time to time.

100 or more years ago, after quarrying huge marble blocks, they would be cut into smaller blocks or slabs by toothless blades of soft iron feed with a slurry of water and sand dragged across the marble surface, back and forth. The abrasive sand was constantly flushed into the cut and beneath the iron blade(s) with water and the source of power would ideally come from a stream or river's flow of water on a waterwheel. Thousands of years ago the ancient Egyptians used copper strips and sand in place of iron and sand to cut blocks of stone. Human power may have been used in place of machine power but the principle was the same, using abrasive sand forced under a moving strip of metal back and forth to cut a groove into a block of stone. The groove becomes a narrow slit as the metal blade cuts deeper into the stone, resulting finally in a flat slab of stone when the blade reaches the bottom of the stone block.
Today, metal blades are inlaid with pieces of diamond and the cut can proceed surprisingly fast. Water is still used as the lubricant and coolant. Usually a rotating circular blade of metal is used with diamond inlaid all along its edge, but also long flat strips of strong metal that are inlaid with diamond on the edge of one side of the metal strip are used, very much the same as a century and several thousand years ago, the difference being the silica sand is replaced by diamond "sand" and the engine powering the movement is stronger and more complex.

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Nov 23, 2024

Nice and shiny white; really nice! Thanks!

SDG

Sep 7, 2023

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Jun 26, 2023

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