Color is the most noticeable factor about gemstones. However, color alone is not the way gemstones are identified and categorized. All gemstones have a unique crystal structure and typical physical and optical properties.

 Natural, transparent gemstones are usually minerals. Minerals can be classified by species, variety and sometimes by group. 

A mineral species is defined by their common chemical compositions and crystal structures. Examples of mineral species include Beryl, Corundum and Quartz. Variety is a sub-division of species and is based on color, transparency or phenomenon (Asterism, Chatoyancy, Play of Color). Examples of mineral varieties include Emerald, Ruby and Citrine. A group consists of two or more mineral species that are similar in chemical composition, crystal structure and properties. Some gems are not minerals either because they are organic gemstones (pearls) or are not natural.  

Beryl

Emerald, Aquamarine, Morganite

Emerald is the most popular and well-known Beryl variety, followed by Aquamarine and Morganite. There are lesser-known varieties as well such as Heliodor (yellow), Maxixe (Blue) and Red Beryl.  

Browse EmeraldBrowse AquamarineBrowse Morganite
VarietyEmeraldAquamarineMorganite
Group/SpeciesBerylBerylBeryl
BirthstoneMayMarch
Hardness7.5-8.07.5-8.07.5-8.0
SourcesColombia, Zambia, Brazil, Central Asia (Pakistan, Afghanistan)Brazil, China, Pakistan Brazil, Mozambique, Namibia, USA 
Desirable ColorBluish Green to pure green with vivid saturation Moderately strong, medium-dark blue to slightly greenish blue Strong Pink
TreatmentClarity Enhancement Heat Treatment Heat Treatment, Irradiation 

Corundum

Ruby, Sapphire

Ruby and Sapphire make up the corundum species and are one of the two most popular gemstones. Ruby is the red variety of Corundum whereas Sapphire comes in rainbow colors with Blue Sapphire being the most popular.  

Browse RubyBrowse Sapphire
VarietyRubySapphire
Group/SpeciesCorundum Corundum 
BirthstoneJulySeptember
Hardness99
SourcesMyanmar (Burma), Mozambique, Madagascar, Sri Lanka, Vietnam, East Africa Madagascar, Sri Lanka, Myanmar (Burma), Kashmir, Thailand, Australia, East Africa 
Desirable ColorPure, vibrant Red to slightly Purplish Red with medium to medium-dark tone and vivid saturation Velvety Blue to Violetish Blue, medium to medium-dark tones, with strong to vivid saturation 
TreatmentHeat Treatment, Glass Filling, Lattice Diffusion, Flux Healing Heat Treatment, Glass Filling, Flux Healing, Lattice Diffusion 

Tourmaline

Tourmaline is one of the most commercially important gemstones and comes in a multitude of colors. Tourmaline comes in vibrant colors from rich reds to pastel pinks, intense greens, deep blues and vivid yellows. Paraiba tourmalines are copper bearing tourmalines and come in neon blues and green colors. They demand one of the highest per carat prices in gemstones.  

Browse Tourmaline
VarietyTourmaline 
Group/SpeciesTourmaline 
BirthstoneOctober
Hardness7-7.5
SourcesBrazil, Mozambique, Nigeria, East Africa 
Desirable ColorAll colors, medium to medium-dark tones and vivid saturation 
TreatmentHeat Treatment, Irradiation 

Garnet

Like Tourmaline, Garnet also belongs to the same mineral group with the same crystal structure but slightly different chemical compositions which gives it different colors. The most important Garnet species in gemstones are: Pyrope, Almandine, Spessartine, Grossular and Andradite. Some examples of Garnet varieties include: 

SpeciesVariety
Andradite Demantoid Garnet 
Grossular Tsavorite 
Pyrope-Almandine Rhodolite 
Browse Garnet
VarietyGarnet 
Group/SpeciesPyrope, Almandine, Spessartine, Grossular and Andradite 
BirthstoneJanuary
Hardness6.5-7.5
SourcesTanzania, Madagascar, Nigeria, Russia, Namibia, Brazil, Kenya 
Desirable ColorAll colors, medium to medium-dark tones and vivid saturation 
TreatmentOften Untreated 

Opal

Opals are known for their inspiring play of colors which occurs due to the interaction of white light with their orderly internal molecule structure. Opals come in many types and are categorized by their background (body color) color. Common opal types are Black opals, White Opals, Water Opals, Fire Opals and Boulder Opals.  

Browse Opal
VarietyOpal 
Group/SpeciesOpal 
BirthstoneOctober 
Hardness5-6.5 
SourcesAustralia, Ethiopia, Mexico, Brazil, USA
Desirable ColorBlack, White, Water, Fire
TreatmentDoublet/Triplets, Gilson Imitation, Synthetic Opal

Tanzanite

Tanzanite was first discovered in 1967 by a Masai Tribesmen in Merelani Hills, Tanzania. Its name was given by Tiffany and Co., inspired by the country it was discovered in. Since its discovery and heavy promotion, Tanzanite has become one of the most popular gemstones.

Browse Tanzanite
VarietyTanzanite 
Group/SpeciesZoisite 
BirthstoneDecember  
Hardness6-7 
SourcesTanzania 
Desirable ColorStrongly saturated pure Blue or Violetish Blue 
TreatmentImitations include Forsterite, Tanavyte 

Spinel

Historically many gemstones had been misidentified as Rubies however were later on recognized as Spinel. Spinel comes in variety of colors from reds, pinks to shades of purple, blue and bluish green.  

Browse Spinel
VarietySpinel 
Group/SpeciesSpinel  
BirthstoneAugust 
Hardness8
SourcesMyanmar (Burma), Sri Lanka, Vietnam, Tajikistan, Tanzania 
Desirable ColorRed is the most rare and desirable Spinel color 
TreatmentRarely treated however red or pink spinels might be heat treated, Synthetic Spinel 

ChrYsoberyl

Alexandrite, Cat's Eye ChrYsoberyl

Alexandrites and Cat’s Eye Chrysoberyl are two of the most rare and popular phenomenal varieties of the Chrysoberyl species. Alexandrites are known for their color-changing phenomenon whereas Cat’s Eye Chrysoberyl display spectacular chatoyancy (cat’s eye).  

Browse AlexandriteBrowse Cat's Eye Chrysoberyl
VarietyAlexandrite Cat’s Eye Chrysoberyl 
Group/SpeciesChrysoberyl Chrysoberyl  
BirthstoneJune 
Hardness8.59
SourcesRussia, Brazil, Sri Lanka, East Africa Sri Lanka, Brazil, Myanmar, Zimbabwe, Madagascar, Tanzania 
Desirable ColorGreen to Bluish Green in daylight changing to Red to Purplish Red in incandescent light Semi-transparent golden yellow to slightly greenish yellow or brownish yellow “honey” color 
TreatmentSynthetic Alexandrite, Synthetic Color-Change Spinel and Corundum Glass Imitations, Cat’s Eye Quartz, Tiger’s Eye Quartz 

Jadeite

Jadeite has been a treasured gemstone for thousands of years especially in Asia. Jade comes in a variety of colors however green is the most popular and valuable.  

Browse Jadeite
VarietyJadeite 
Group/SpeciesJadeite 
Birthstone
Hardness6-7
SourcesMyanmar (Burma) 
Desirable ColorSemi-transparent with even, vivid-green coloration 
TreatmentImpregnation (Polymers), Dyeing, Heat Treatment 

Organic Gems

Coral, Pearl

Organic gemstones are gemstones that are derived from living matter I.e., from plants or animals. Examples include Pearl and Coral. As organic gems are derived from plants or animals, environmental concerns led to a global treaty called CITES. Its purpose was to protect the environment from unregulated trade.  

Browse CoralBrowse Pearl
VarietyCultured Pearl Coral 
Group/SpeciesCultured Pearl Calcerous Coral 
BirthstoneJune 
Hardness2.5-33-4
SourcesJapan, China, Pacific (Tahitian Pearls), South East Asia Mediterranean Sea (Italy), Japan, South East Asian Waters 
Desirable ColorPearls occur in a broad range of colors Intense Red (Oxblood) 
TreatmentLuster Enhancement, Dyeing, Coating, IrradiationColor Impregnation, Dyeing, Glass and Porcelain Imitations