All natural rubies have imperfections in them, including color impurities and inclusions of rutile needles known as "silk". Gemologists use these needle inclusions found in natural rubies to distinguish them from synthetics, simulants, or substitutes. Usually the rough stone is heated before cutting. Almost all rubies today are treated in some form (of which heat treatment is the most common practice), and rubies which are completely untreated and still of excellent quality command a large premium. In general we can list the following types of improvements: color alteration, improving transparency by dissolving rutile inclusions, healing of fractures (cracks) or even completely filling them. See Treatments below.
Prices of rubies are primarily determined by color (the brightest and best "red" called Pigeon Blood Red, command a huge premium over other Rubies of similar quality). After Color follows clarity: similar to Diamonds, a clear stone will command a premium, but a Ruby without any needle-like rutile inclusions will indicate the stone has been treated one way or another. Cut and Carat (size) also determine the price approximately like clarity does.

14k Gold Pearl and Ruby Earrings

$49.25 from OrkydPearls.com - A dainty gem. A nice 5-5.6mm Akoya cultured pearl is accompanied by a bright red Ruby and set in yellow gold. A charming pair of earrings that promises to enlighten her face and enhance her beauty.

Ruby and 6 Diamond Channel Stone Ring

$395.00 from Szul.com - Uniquely Elegant. This beautifully crafted Diamond and ruby Ring features a glorious 6x4mm center oval prong set ruby with 2 side ruby stones along with sparkling channel set diamonds.

Royal Ruby and Baguette Pendant

$275.00 from Szul.com - One lovely, oval ruby rests at the harmonious center of a wider oval of shimmering diamond baguettes. Sleek, refined 14 karat yellow gold is cleanly crafted into a graceful bail and frames the ruby gemstone.

Ruby and Diamond Bracelet 14K Yellow Gold

$695.00 from Szul.com - This masterfully crafted 14 karat yellow gold bracelet drips with rich color and sparkle. Prong-set ruby ovals alternate with 20 sparkling, round diamonds for slender, sensual style. Simply elegant piece!

Diamond and Ruby Heart Pendant

$125.00 from Szul.com - This pretty heart pendant is alive with radiance and precious color. Gracefully crafted 10 karat yellow gold is hugged by alternating prong-set rubies and diamonds. Sweet and richly colorful.

Ruby and Diamond Right Hand Ring

$395.00 from Szul.com - A new twist to the new Diamond Right Hand Ring collection. This spectacular piece showcases a combination of sparkling diamonds and enchanting natural ruby gemstones on a stylish Right Hand Ring band.

Genuine Ruby 14k Stud Earrings
This pair of genuine ruby gemstones was set in 14k yellow gold stud earrings. These lovely ruby gemstones are moderately included (GIA: Type II Gem: Clarity Grade SI), and they have very beautiful deep red color under incandescent light as shown in the photo at left. They were faceted from natural ruby crystals that were mined in Madagascar! They were carefully heated and have natural inclusions which absolutely guarantee their natural origin.
Weight: Ruby Gems weigh 1.35 carat total weight
Size: 6.2mm x 4.2mm faceted ovals
Location: Faceted from genuine ruby crystals mined in Madagascar
Price: $431.25

Faceted Translucent Ruby Sterling Silver Ring
This size 9 ring was handcrafted in sterling silver and set with a 15x11mm feceted gemstone of genuine ruby weighing 10 carats. This oval shaped ruby gem is translucent and has very rich purplish-red color(100% natural color, unheated and untreated). The inset photo shows this ring back-lit to better show its translucency.
Size: Ring size 9
Price: $64.95

Ruby in Zoisite Sterling Silver Pendant
This pendant was handcrafted in sterling silver and set with a 18x15mm rectangular shaped ruby in zoisite cabochon gem that was ground & polished from natural ruby in zoisite rough mined in Tanzania, Africa.
Size: 1.4" x 0.6" (37.5mm x 17mm)
Price: $36.50

Ruby in Zoisite Sterling Silver Bracelet

This ruby in zoisite bracelet was handcrafted in sterling silver and set with five natural oval shape ruby cabochon gemstones ranging in size from 29x18mm up to 34x28mm. The photo at left is viewed under incandescent light.
Size: Adjustable length from 7.5" to 8.75" long
Price: $182.50


General
Category Mineral variety
Chemical formula aluminium oxide with chromium, Al2O3::Cr
Identification
Color Red, may be brownish or purplish
Crystal habit Varies with locality. Terminated tabular hexagonal prisms.
Crystal system Trigonal
Cleavage No true cleavage
Fracture Uneven or conchoidal
Mohs Scale hardness 9.0
Luster Vitreous
Refractive index ~1.762-1.770
Pleochroism Orangy Red, Purplish Red
Ultraviolet fluorescence red under longwave
Streak white
Specific gravity 4.0
Melting point 2050°C
Fusibility perfectly
Solubility none
Diaphaneity transparent