Gemstone Measurements & Quality Guide: How to Choose the Perfect Stones for Jewelry & Navratna

Navratna & Jewelry Gemstone Buying Guide: Carats, Size, Color, and Quality Explained

When it comes to choosing gemstones—especially for Navratna jewelry—understanding measurements, weight, and quality parameters is key to ensuring both beauty and spiritual effectiveness. 

Whether you're buying a single-stone piece or a nine-gem Navratna set, these factors help you select stones that are authentic, well-cut, and astrologically powerful.

Gemstones: Carats, Size, Color, and Quality

1. Weight: Carats (ct)

Gemstone weight is measured in carats, with 1 carat equaling 200 milligrams (0.2 grams). While carat affects size, the stone’s cut and shape also influence how large it appears. For example, a 1 ct round diamond is about 6.5 mm in diameter, but a 1 ct ruby or sapphire may vary depending on its cut.

2. Size: Millimeters (mm)

Gemstones are also measured in millimeters for length, width, and depth. This is especially important when designing custom jewelry. Common examples include:

• Round cut: ~6.5 mm for 1 carat, most common, symmetrical

• Oval cut: ~7 × 5 mm for 1 carat, slightly larger surface area

• Emerald cut: ~7 × 5 mm for 1 carat, rectangular, step cuts

• Pear cut: ~8 × 5 mm for 1 carat, teardrop shape

• Cushion cut: ~6 × 6 mm for 1 carat, rounded square shape

 

3. Purity / Clarity

Clarity refers to inclusions—tiny imperfections inside or on the surface of the gemstone. For spiritual and Navratna jewelry, eye-clean stones (no visible flaws to the naked eye) are preferred, although small natural inclusions are acceptable. 

Gemstones are graded from IF (Internally Flawless) to I (Included) based on how visible the inclusions are.

• IF (Internally Flawless) – No visible inclusions under 10× magnification.
• VVS (Very Very Slightly Included) – Minute inclusions, hard to see.
• VS (Very Slightly Included) – Minor inclusions visible under magnification.
• SI (Slightly Included) – Noticeable inclusions under magnification and sometimes to the naked eye.
• I (Included) – Obvious inclusions may affect durability.

4. Color

Color is a critical factor for both beauty and astrological potency. For Navratna:

• Ruby: Deep, vibrant red with no brownish tint

• Emerald: Rich, pure green without a yellowish tint

• Sapphire: Deep, even blue

A gemstone’s tone and saturation can greatly influence its perceived value and spiritual strength.

 

5. Cut & Shape

A well-cut gemstone maximizes light reflection and enhances brilliance. Navratna jewelry often features cabochon cuts (smooth, rounded, non-faceted) for stones like Pearl, Hessonite, and Cat’s Eye, while Ruby, Sapphire, Emerald, and Diamond are typically faceted cuts for sparkle.

6. Other Quality Factors

• Treatment: Some stones are heat-treated or enhanced for color or clarity. Natural, untreated stones are best for astrology.

• Origin: Famous mines like Kashmir (Sapphire) or Colombia (Emerald) increase value.

• Certification: Always request a gem lab certificate (GIA, IGI) to verify authenticity, weight, and quality.

 

Navratna Gemstone Quality Reference Table

Gemstone ➞ Ideal Weight ➞ Size (mm) ➞ Preferred Cut ➞ Purity Notes

• Ruby ➞ 1–3 ct ➞ 6–8 mm ➞ Faceted (Oval/Round) ➞ Eye-clean, rich red

• Pearl ➞ N/A ➞ 6–10 mm ➞ Smooth Cabochon ➞ Lustrous, no cracks

• Red Coral ➞ 1–5 ct ➞ Varies ➞ Smooth Cabochon ➞ Deep red/orange, natural

• Emerald ➞ 1–3 ct ➞ 6–8 mm ➞ Emerald cut/Oval ➞ Minimal inclusions, rich green

• Yellow Sapphire ➞ 1–3 ct ➞ 6–8 mm ➞ Faceted (Oval) ➞ Bright yellow, clear

• Diamond ➞ 1–2 ct ➞ 6–6.5 mm ➞ Round Brilliant ➞ High clarity, D-F color preferred

• Blue Sapphire ➞ 1–3 ct ➞ 6–8 mm ➞ Faceted (Oval/Round) ➞ Deep blue, eye-clean

• Hessonite ➞ 1–3 ct ➞ 6–8 mm ➞ Smooth Cabochon ➞ Honey-orange color

• Cat’s Eye ➞ 1–3 ct ➞ 6–8 mm ➞ Smooth Cabochon ➞ Sharp “eye” effect

FAQs

1. What is the best carat weight for Navratna gemstones?
For Navratna rings, most gemstones range from 1–3 carats each, depending on design and finger size.

2. How do I check gemstone clarity for Navratna jewelry?
Look for eye-clean stones with no visible inclusions. Certification from GIA or IGI ensures clear grading.

3. Which gemstone cut is best for astrology purposes?
Cabochon cuts are ideal for Pearl, Hessonite, and Cat’s Eye, while faceted cuts suit Ruby, Sapphire, Emerald, and Diamond.

4. Does gemstone origin matter for spiritual benefits?
Yes. Stones from renowned origins like Kashmir (Sapphire) or Colombia (Emerald) are often considered more powerful.

5. Should I buy treated or untreated gemstones for astrology?
Untreated, natural gemstones are always preferred for maximum astrological and spiritual benefits.

Key Takeaways From This Post:

• How to measure gemstones in carats and millimeters
• Best gemstone clarity grades for Navratna jewelry
• Ideal color and cut for each Navratna gemstone
• Difference between faceted and cabochon cuts
• Why gemstone certification is important