S is for Sapphire

Sapphire is a precious gemstone of the mineral corundum, an aluminum oxide.  Sapphire is typically blue, but natural “fancy” sapphires can be yellow, purple, orange and green, or “parti sapphires,” which are two or more of these colors.  The only color sapphire can’t be is red because red corundums are rubies.  The variety in color is from trace amounts of iron, titanium, chromium, copper, or magnesium.

This beauty is the Logan Sapphire and it weighs 423 carats - Wikipedia

Sapphires are usually cut and polished into gems and worn as jewelry although they can also be used in wristwatch crystals, high-durability windows and thin electronic wafers among other things.  Sapphire, like ruby, is also a 9.0 on Mohs scale of hardness.

A cut and polished sapphire gemstone - Wikipedia

Sapphire is graded like other gemstones, as mentioned before, by color, cut, clarity and carat weight.  The color of gemstones can be described in terms of hue, saturation and tone.  Hue is the “color” of the gemstone.  Saturation is brightness of the hue and tone is the lightness and darkness of the hue.

A beautiful teardrop cut sapphire - Wikipedia

Green or gray lessens the hue considerably and also the value.  Ideally it’s best to have violet or purple contribute to the intensity of the blue color of sapphires.

Here’s an interesting tidbit about parti sapphires.  Australia is the largest source of particolored sapphires.  These aren’t typically used in jewelry so are relatively unknown.  Particolored sapphires cannot be created synthetically and only occur naturally.

A padparadscha sapphire - Wikipedia

Naturally formed pink-orange corundum is very rare.  This type of sapphire is called Padparadscha.  This name comes from the name for the lotus flower as this is much the same color.  These stones are often from Sri Lanka.  Orange gems are often higher in price than the highest quality blue sapphire.  Because of heat treatment called lattice diffusion, more of these orange gems are being seen in the marketplace, but the naturally occurring ones are the most valuable.

Star sapphire - Wikipedia

The star sapphire exhibits a star pattern when viewed from a single overhead light source.  This star is due to rutile inclusions in the stone when it was formed.  As discussed earlier, rutile is titanium dioxide.  These gems are generally cut into cabochons (flat on the bottom) and mounted that way with the star facing outward.  The red stones like this are called “star rubies.”

Sapphire is the birthstone for September and also the gem for a forty-fifth anniversary.