GemTrove
Gemstone Properties: Hardness, RI, SG, Durability and Jewellery Use
GemTrove explains gemstone hardness, refractive index, specific gravity, toughness, treatment, origin and jewellery suitability for coloured gemstone buyers.
Gemstone Properties Guide
Gemstone Properties: Hardness, RI, SG, Durability and Jewellery Use
Gemstones are not chosen by colour alone. Hardness, toughness, refractive index, specific gravity, treatment, origin and cutting quality all affect how a gemstone looks, wears and performs in jewellery.
This GemTrove guide explains the key gemstone properties customers should understand before choosing coloured gemstones for rings, pendants, necklaces, earrings, bracelets or custom-made jewellery.
Quick Answer
Which gemstone properties matter most for jewellery?
Colour is only one part of gemstone selection. Hardness, toughness, cleavage, treatment, setting style and jewellery use all matter. A gemstone can be hard enough to resist scratches but still vulnerable to chipping, impact or treatment-related care issues.
Why It Matters
Why Gemstone Properties Matter
A gemstone may look beautiful, but beauty alone does not tell the full story. Some gems are excellent for daily rings, while others are better suited to pendants, earrings or occasional wear.
A sapphire used in an everyday ring needs different consideration from an opal used in a pendant or an emerald used in a dress ring.
Gemstone Properties
Key Gemstone Properties Explained
Gemologists use several properties together when identifying and assessing gemstones. No single property should be used alone.
| Property | What it means | Why it matters |
|---|---|---|
| Mohs hardness | Resistance to scratching on a scale from 1 to 10 | Important for rings and bracelets that receive regular wear |
| Toughness | Resistance to breaking, chipping or cracking | Some gems are hard but brittle or vulnerable to cleavage |
| Refractive index | How strongly light bends as it enters the gemstone | Helps identification and visual performance assessment |
| Specific gravity | Relative density of the gemstone | Useful for separating gems that may look similar |
| Birefringence | Difference between two refractive indices in doubly refractive gems | Can help identify gems and visual softness |
| Pleochroism | Different colours seen from different crystal directions | Important when cutting and orienting for best colour |
| Cleavage | A tendency to split along certain crystal directions | Affects setting protection and wear advice |
| Treatment | Enhancement such as heating, oiling, filling or diffusion | Affects value, care and cleaning methods |
| Origin | Geographic source of a gemstone | May influence rarity and value in some stones |
Reference Table
Gemstone Hardness, RI and SG Reference
The values below are general educational references. Natural variations, treatments, inclusions and testing conditions can affect assessment.
| Gemstone | Mohs hardness | Typical RI | Typical SG | Jewellery suitability |
|---|---|---|---|---|
| Diamond | 10 | 2.417 | 3.52 | Excellent for rings and bracelets |
| Sapphire / Ruby | 9 | 1.760–1.770 | 3.99–4.05 | Excellent for daily wear with good setting |
| Alexandrite / Chrysoberyl | 8.5 | 1.746–1.755 | 3.70–3.78 | Very good for rings depending on stone |
| Spinel | 8 | 1.718 | 3.58–3.61 | Strong jewellery choice |
| Emerald | 7.5–8 | 1.565–1.602 | 2.67–2.78 | Beautiful but needs care |
| Aquamarine / Morganite | 7.5–8 | 1.577–1.583 | 2.68–2.80 | Good for rings with care and pendants |
| Garnet | 6.5–7.5 | Varies by species | 3.50–4.30 | Good for many designs depending on variety |
| Tourmaline | 7–7.5 | 1.614–1.666 | 3.02–3.26 | Popular for colour; needs sensible care |
| Opal | 5.5–6.5 | 1.37–1.52 | 1.98–2.25 | Best for protected jewellery |
| Pearl | 2.5–4.5 | Approx. 1.52–1.69 | Approx. 2.60–2.85 | Best for earrings and necklaces |
Jewellery Suitability
Best Gemstones for Different Jewellery Types
| Jewellery type | Good gemstone choices | Extra care needed |
|---|---|---|
| Everyday rings | Diamond, sapphire, ruby, spinel, selected chrysoberyl | Emerald, tanzanite and opal need protective settings |
| Engagement rings | Diamond, sapphire, ruby and selected durable coloured gemstones | Consider hardness, toughness, setting protection and long-term wear |
| Pendants and necklaces | Most gemstones including emerald, aquamarine, morganite, opal, pearl and tanzanite | Less impact than rings but still avoid harsh cleaning |
| Earrings | Most gemstones because earrings receive less wear | Match colour and weight carefully |
| Bracelets | Diamond, sapphire, ruby and tougher stones | Bracelets receive knocks and need strong protection |
In-House Assessment
GemTrove’s In-House Gemstone Assessment
GemTrove uses practical jewellery knowledge together with in-house gemological instruments to help assess gemstones. This may include magnification, refractive index testing, polariscopic observation, specific gravity assessment where suitable, UV reaction, Chelsea filter observation, spectroscopy, diamond testing and advanced diamond screening.
For custom jewellery and remodelling, gemstone STL scanning may also assist with understanding stone proportions and planning settings where relevant.
Gem identification
Properties help separate natural, synthetic, treated and imitation materials.
Jewellery suitability
Durability, setting style and wear habits are considered before recommending a gemstone.
Custom design support
Stone shape, measurements, proportions and durability guide CAD design and setting choice.
Frequently Asked Questions
Helpful customer questions
What are gemstone properties?
Gemstone properties are the physical and optical features used to understand, identify and assess a gem, including hardness, toughness, refractive index, specific gravity, birefringence, pleochroism, cleavage, treatment, origin and inclusions.
Is hardness the most important gemstone property?
Hardness is important, but it is not the only factor. It measures scratch resistance, while toughness relates to resistance against breaking or chipping.
What is refractive index in gemstones?
Refractive index, often called RI, measures how light bends as it enters a gemstone. It helps identify gemstones and relates to brilliance and appearance.
What is specific gravity in gemstones?
Specific gravity, or SG, is relative density. It can help separate stones that look similar but have different mineral compositions when used with other tests.
Which gemstones are best for everyday rings?
Diamond, sapphire and ruby are among the most practical choices. Spinel and selected chrysoberyl can also be strong choices. Softer stones need protective settings and careful wear.
Is emerald suitable for everyday wear?
Emerald can be worn in rings, but it needs care because many emeralds contain inclusions and are commonly oiled. Protective settings and gentle cleaning are important.
Can GemTrove help identify my gemstone?
GemTrove can inspect gemstones using in-house gemological instruments and provide practical guidance. For complex cases, independent laboratory reports may also be recommended.
Do gemstone treatments affect value?
Yes. Treatments can affect value, care and transparency. Heating may be common in sapphire, while filling or dyeing can have stronger effects on durability and value.
Does gemstone origin matter?
Origin can matter for fine ruby, sapphire and emerald, but colour, clarity, cut, size, treatment and overall quality remain major value factors.
Can I use coloured gemstones in engagement rings?
Yes, but the gemstone choice must be practical. Sapphire and ruby are strong options, while emerald, opal, tanzanite and softer stones require more care.
Next Step
Choose the Right Gemstone with GemTrove
Whether you are creating a gemstone ring, pendant, necklace, bracelet or remodelling an existing piece, GemTrove can guide you through gemstone properties, durability, treatments and jewellery suitability.