The Complete Gemstone Guide

From precious stones like rubies and sapphires to a rainbow of semi-precious options, our comprehensive guide will help you understand and appreciate the beauty, value, and unique characteristics of gemstones.

Precious Gemstones

Historically, only rubies, sapphires, emeralds, and diamonds were considered "precious" gemstones due to their rarity, hardness, and cultural significance. Though the precious/semi-precious distinction is less relevant in modern gemology, these stones continue to be highly valued for their beauty and durability.

Ruby

Known for its deep red color, ruby is a variety of the mineral corundum and one of the most valuable gemstones.

Color:

Red (from light pink to deep crimson)

Hardness:

9 on Mohs scale

Birth Month:

July

Value Factors:

Color (deep "pigeon blood" red is most prized), clarity, size, and origin

Care Level:

Low maintenance; suitable for daily wear

Sapphire

Another variety of corundum, sapphires come in all colors except red (which would be ruby). Blue sapphires are the most popular and valuable.

Color:

Most commonly blue, but available in nearly all colors including pink, yellow, green, purple, and colorless

Hardness:

9 on Mohs scale

Birth Month:

September

Value Factors:

Color (royal blue most valued), clarity, size, and origin

Care Level:

Low maintenance; suitable for daily wear

Emerald

A variety of beryl, emeralds are prized for their lush green color and historical significance.

Color:

Green (from light to deep rich green)

Hardness:

7.5-8 on Mohs scale

Birth Month:

May

Value Factors:

Color (vivid, slightly bluish-green is most valuable), clarity, size, and minimal treatments

Care Level:

Requires careful handling; avoid impacts and harsh chemicals

Semi-Precious Gemstones

"Semi-precious" encompasses all other gemstones beyond the traditional "precious" ones. Many of these stones can be more rare, valuable, and beautiful than some "precious" gems, demonstrating the outdated nature of this classification. These gems offer a wider range of colors, properties, and price points.

Amethyst

Purple variety of quartz, once considered as valuable as rubies until large deposits were discovered.

Color:

Purple (from pale lilac to deep purple)

Hardness:

7 on Mohs scale

Birth Month:

February

Care:

Moderate; avoid prolonged sunlight exposure

Aquamarine

A blue to blue-green variety of beryl, named after the Latin words for "sea water".

Color:

Light blue to blue-green

Hardness:

7.5-8 on Mohs scale

Birth Month:

March

Care:

Moderate; avoid high heat and harsh chemicals

Topaz

Classic gemstone available in various colors, with blue topaz being the most popular commercially.

Color:

Colorless, blue, brown, yellow, pink, purple, red (rare)

Hardness:

8 on Mohs scale

Birth Month:

November

Care:

Moderate; can crack if exposed to rapid temperature changes

Opal

Known for its unique play of colors, opal contains microscopic spheres that diffract light to create flashes of color.

Color:

White, black, or fire opal with spectacular play of colors

Hardness:

5.5-6.5 on Mohs scale

Birth Month:

October

Care:

High; avoid water, heat, and impacts

Peridot

One of the few gemstones that occurs in only one color, varying from yellowish-green to olive.

Color:

Yellow-green to olive-green

Hardness:

6.5-7 on Mohs scale

Birth Month:

August

Care:

Moderate; avoid high heat and sudden temperature changes

Garnet

A group of minerals with similar properties but varying in chemical composition and color.

Color:

Most commonly red, but also green, orange, yellow, purple, and color-changing

Hardness:

6.5-7.5 on Mohs scale

Birth Month:

January

Care:

Low to moderate; generally durable

Understanding Gemstone Treatments

Most gemstones on the market today undergo some form of treatment to enhance their appearance. These treatments are accepted practices in the industry when properly disclosed to the buyer. Understanding common treatments helps you make informed decisions and properly care for your gems.

Treatment	Description	Common For	Disclosure Impact
Heat Treatment	Heating gemstones to enhance or change color, improve clarity, or alter other characteristics.	Sapphires, rubies, aquamarine, amethyst, topaz, tanzanite	Standard and widely accepted with proper disclosure
Oiling/Filling	Filling surface fractures with oils, resins, or glass to improve clarity and appearance.	Emeralds (oil), rubies (lead glass), diamonds (fracture filling)	Must be disclosed; significantly affects value compared to untreated stones
Irradiation	Exposing gemstones to radiation to alter their color.	Blue topaz, certain diamonds, tourmaline, pearl	Must be disclosed; regulated by various authorities
Dyeing	Adding coloring agents to porous gemstones to change or enhance color.	Pearls, corals, turquoise, jade, onyx	Must be disclosed; reduces value compared to natural counterparts
Surface Coating	Applying thin layers of chemicals to alter or enhance a gemstone's color or appearance.	Topaz, quartz, tanzanite simulants	Must be disclosed; significantly reduces value

Gemstone Buying Tips

Whether you're buying gemstones for investment, a special occasion, or simply because you love their beauty, these expert tips will help you make informed decisions.

Certification Matters

For significant purchases, especially colored gemstones of high value, look for stones with certificates from reputable laboratories like GIA, AGL, or SSEF. These provide unbiased information about the stone's characteristics and any treatments.

Consider Durability

If purchasing for everyday wear like an engagement ring, prioritize gemstones with higher hardness (7+ on Mohs scale) such as sapphires, rubies, or spinel. Softer stones like opals (5.5-6.5) or pearls (2.5-4.5) are better suited for occasional wear or protected settings.

Prioritize Color

For colored gemstones, color is typically the most important value factor. Look for stones with vivid, rich colors in the hue most desirable for that specific gemstone variety. In general, stones with medium-dark tone (not too light or too dark) and high saturation are most valuable.

Frequently Asked Questions

What's the difference between precious and semi-precious gemstones?

Historically, only diamonds, rubies, sapphires, and emeralds were classified as "precious" gemstones, with all others considered "semi-precious." This distinction originated in ancient times based on rarity and value, but is considered outdated by modern gemologists. Today, many "semi-precious" stones like fine alexandrite, spinel, or Paraíba tourmaline can be more valuable than some "precious" stones. The quality, rarity, and size of individual stones are more important factors than this traditional classification.

Are synthetic gemstones "fake"?

Synthetic gemstones are not "fake"—they have the same chemical composition, crystal structure, and optical properties as their natural counterparts. They're real gemstones created in laboratories rather than mined from the earth. Synthetics differ from simulants (like cubic zirconia or glass), which only mimic the appearance of another gemstone but have different chemical and physical properties. Synthetic gemstones offer excellent quality and environmental benefits at lower prices, though they lack the rarity and historical value of natural stones.

How should I care for my gemstone jewelry?

Care requirements vary by gemstone. As a general rule, clean most hard gemstones (sapphires, rubies, garnets) with mild soap, warm water, and a soft brush. Softer or more porous stones (emeralds, opals, pearls, turquoise) should never be soaked and should be wiped with a damp, soft cloth. Store gemstone jewelry separately to prevent scratching, and remove before activities like swimming, cleaning, or sports. For valuable pieces, have them professionally cleaned and inspected annually to ensure settings remain secure.

What gemstones work well for engagement rings?

Beyond diamonds, sapphires are an excellent choice due to their durability (9 on Mohs scale) and variety of colors. Rubies offer similar hardness with romantic red hues. Moissanite has become popular for its diamond-like brilliance and exceptional hardness (9.25). For colored options with good durability, consider spinel, alexandrite, or garnet varieties like tsavorite. While beautiful, emeralds, aquamarines, and tanzanites (7-8 hardness) require more careful wear. Avoid soft stones like opals, pearls, or turquoise for daily-wear rings.

How can I tell if a gemstone is natural or treated?

Without specialized equipment, identifying treatments can be challenging even for professionals. The best approach is to purchase from reputable dealers who provide full disclosure and certification from recognized laboratories (GIA, AGL, etc.) for valuable stones. Most colored gemstones on the market are treated in some way—completely untreated natural rubies, sapphires, and emeralds of good quality are rare and command significant premiums. When in doubt, have important pieces evaluated by an independent appraiser or gemological laboratory.

Ready to explore our gemstone collection?

Discover our selection of fine gemstone jewelry, from classic precious stone pieces to unique designs featuring exceptional colored gemstones. Our expert jewelers can also create custom pieces featuring your favorite gemstones.

Browse Gemstone Jewelry Schedule a Consultation