Diamond and Graphite & Sapphire and Ruby: We are family…

“A diamond is forever. Diamond is the lifelong dream of women”, most of the people say.

Recently, I always miss my cousin. I kept thinking back to the day I accompanied her to buy her diamond wedding ring on February. The ruby, together with the sapphire, the emerald, and the diamond are considered of the four precious stones. Those embedded in jewellery have soft shade of colours and glittered attractively in the sunlight; you must have a sudden impulse to own those.
A diamond is forever, it means everlasting love and life. But, it is a lie due to the chemical properties of Carbon. So, what is the relation between glittering jewels and dull graphite?

Corundum
Corundum is a crystalline form of aluminium oxide (Al2O3) with traces of iron, titanium and chromium. Corundum is a very hard, tough, and stable rock-forming mineral. It is one of the naturally clear transparent materials, but can have different colors when impurities are present. Rubies are red corundum and corundum of any other color is known as sapphires.
Corundum is very hard. Due to a Mohs Scale hardness of nine (pure corundum is defined to have 9.0 Mohs), it is the second hardest mineral known, with diamond being the only harder mineral. It can scratch almost every other mineral.

Crystal structure of corundum
It is in the trigonal subdivision of the hexagonal crystal system, which is reflected in the commonly found hexagonal prismatic crystal form.

----SAPPHIRES----

In scientific terms, the name Sapphire refers to all varieties of Corundum excluding Ruby and Emery. In gem terms, deep blue corundum is known as "sapphires". Sapphire is the September birthstone and for the 5th and 45th anniversary gemstone gifts.
Corundum that is contaminated with iron or titanium has a blue color. Sapphire is the most precious of blue gemstones due to its color, hardness, durability, and luster. The most valuable color of sapphire is cornflower blue, known as Kashmir sapphire or Cornflower blue sapphire. Sapphire gems displaying asterism are known as "star sapphires".
The color of corundum can be artificially altered by heating to temperatures between 500 and 1800 °C for several hours, or by heating in a nitrogen-deficient atmosphere oven for seven days or more or radiation. This is done by heating the sapphires. The process of creating synthetic sapphire is known as the Verneuil process which fine alumina powder is added to an oxyhydrogen flame which is directed downward against a mantle.
It is used in many applications, including infrared optical components, watch crystals, high-durability windows, and wafers for the deposition of semiconductors.

Star sapphire

A star sapphire is a type of sapphire that exhibits a star-like phenomenon known as asterism. Star sapphires contain intersecting needle-like inclusions (a mineral composed primarily of titanium dioxide ) that cause the appearance of a six-rayed 'star'-shaped pattern when viewed with a single overhead light source.

----Ruby----
This deep red corundum is known as "rubies". Ruby is the July birthstone and 15th and 40 anniversary stone.
Finely colored rubies are one of the most expensive of all gems, because natural flawless ruby is virtually unheard of!

Natural rubies can be evaluated using the four Cs together with their size and geographic origin.
Improvements used include color alteration, improving transparency by dissolving rutile inclusions, healing of fractures (cracks) or even completely filling them. The most common treatment is the application of heat which occurs around temperatures of 1800 °C (3300 °F).
Other processes in which synthetic rubies can be produced are through the Pulling process, flux process, and the hydrothermal process. Rods of synthetic ruby are used to make ruby lasers and masers.

Indian Star Ruby

Some rubies show a 3-point or 6-point asterism or "star". Asterisms are best visible with a single-light source, and move across the stone as the light moves or the stone is rotated.

" Sapphire and ruby are corundum and have the same properties why they appear in different colour?”

• If both titanium and iron impurities are present together, the result is a magnificent deep-blue color. Blue color in sapphires comes from intervalence charge transfer, which is the transfer of an electron from one transition-metal ion to another via the conduction or valence band. The iron can take the form Fe2+ or Fe3+, while titanium generally takes the form Ti4+. If Fe2+ and Ti4+ ions are substituted for Al3+, an electron transfer from Fe2+ and Ti4+ can cause a change in the valence state of both. The wavelength of the energy absorbed corresponds to yellow light. When this light is subtracted from incident white light, the complementary color blue results. Sapphire blue is apparent with the presence of only 0.01% of titanium and iron.


• Ruby is α-alumina (the most stable form of Al2O3) in which a small fraction of the aluminum3+ ions are replaced by chromium3+ ions. Each Cr3+ is surrounded octahedral by six O2- ions. This crystallographic arrangement strongly affects each Cr3+, resulting in light absorption in the yellow-green region of the spectrum and thus in the red color of the gem.
  

Carbon

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are several allotropes of carbon of which the best known are graphite, diamond, and amorphous carbon.

Characteristics

Some allotropes of carbon: a) diamond; b) graphite; c) lonsdaleite; d–f) fullerenes (C60, C540, C70); g) amorphous carbon; h) carbon nanotube.

----Graphite----
The mineral graphite is one of the allotropes of carbon. It is opaque and black. It is an electrical conductor, a semimetal. Graphite is soft enough to form a streak on paper. All the allotropic forms are solids under normal conditions but graphite is the most thermodynamically stable
Thin flakes are flexible but inelastic, the mineral can leave black marks on hands and paper, and it conducts electricity, displays superlubricity.
The two known forms of graphite, alpha (hexagonal) and beta (rhombohedral), have very similar physical properties. The hexagonal graphite may be either flat or buckled. Graphite that naturally occur have been found to contain up to 30% of the beta form, when synthetically-produced graphite only contains the alpha form.
Natural graphite has found uses as the marking material ("lead") in common pencils, in zinc-carbon batteries, in electric motor brushes, and various specialized applications.

Intercalated graphite
Graphite forms intercalation compounds with some metals and small molecules. In these compounds, the host molecule or atom gets "sandwiched" between the graphite layers, resulting in compounds with variable stoichiometry. A prominent example of an intercalation compound is potassium graphite, denoted by the formula KC8.

----Diamond----
Diamond is the allotrope of carbon where the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. Diamond is the April Birthstone. It is highly transparent and has a very low electrical conductivity.Diamond has a high refractive index (2.417) and moderate dispersion (0.044) properties which give cut diamonds their brilliance.
Diamond is the hardest known naturally occurring material, scoring 10 on the Mohs scale of mineral hardness. Those properties determine the major industrial application of diamond in cutting and polishing tools.
Diamond's toughness or tenacity is only fair to good. Toughness relates to the ability to resist breakage from falls or impacts. A diamond will shatter if hit with an ordinary hammer.
Four characteristics, known informally as the four Cs, are now commonly used as the basic descriptors of diamonds: these are carat, cut, color, and clarity.
Diamonds occur in various colors. Colored diamonds contain crystallographic defects, including substitutional impurities and structural defects, which cause the coloration. Theoretically, pure diamonds would be transparent and colorless.

Color in irradiated diamonds, with annealing (two left stones) and without annealing (right)
The formation of natural diamond requires very specific conditions—exposure of carbon-bearing materials to high en approximately 1650–2370 °F (900–1300 °C).

“If Graphite and Diamond are made only of carbon what gives them different properties?” Notice that graphite is layered. Graphite has a sheet like structure where the atoms all lie in a plane. Graphite is strong covalent bonds between carbon atoms in each layer. But, only weak forces exist between layers. Graphite is a layered compound. In each layer, the carbon atoms are arranged in a hexagonal lattice with separation of 0.142 nm, and the distance between planes is 0.335 nm.

Diamond has a framework structure in three dimensions. In diamond each carbon atom is the same distance to each of its neighboring carbon atoms. In this rigid network atoms cannot move. Diamonds crystallize in the diamond cubic crystal system (space group ) and consist of tetrahedrally, covalently bonded carbon atoms. A diamond is a transparent crystal of tetrahedrally bonded carbon atoms (sp3) that crystallizes into the diamond lattice which is a variation of the face centered cubic structure. Each atom is bonded tetrahedrally to four others, thus making a 3-dimensional network of puckered six-member rings of atoms.

The system of carbon allotropes spans a range of extremes:
Actually, you realized that sapphires and ruby are same compound and have same properties but they are in different colour. Graphite and diamond are made only of carbon but they have different looks and properties. So, don’t be cheated again. In our world, there is nothing all the same and everlasting. Like the diamond wedding ring, it was nothing left, even the love and life…