Not all stones are gems, and not all gems are equal. Gemstones are traditionally divided into two categories — precious and semiprecious — based mainly on their rarity, hardness and value. But what exactly separates the two, and which stones belong to each group? This guide explains the difference clearly, with the four precious stones, common semiprecious stones, and how gemstones are classified.
What Are Gemstones?
A gemstone is a mineral (or, in some cases, an organic material like pearl) that is cut and polished for use in jewellery and ornamentation. To qualify as a gem, a stone should be beautiful, durable and rare — the very qualities that also determine whether it is classed as precious or semiprecious.
How Are Gemstones Classified?
The precious/semiprecious classification is a traditional one, based largely on:
- Rarity — how scarce the stone is in nature
- Hardness — its durability (measured on the Mohs scale)
- Value — its price and desirability
- Beauty — colour, clarity and brilliance
It’s worth noting there is no strict scientific dividing line — the main difference comes down to cost, rarity and durability. Many semiprecious stones are stunning and valuable in their own right.
The 4 Precious Stones
Only four gemstones are traditionally classed as precious:
| Precious Stone | Mineral | Hardness (Mohs) | Colour |
|---|---|---|---|
| Diamond | Pure crystalline carbon | 10 (hardest) | Colourless (and fancy colours) |
| Ruby | Corundum (chromium) | 9 | Red (rose to deep crimson) |
| Sapphire | Corundum (iron/titanium) | 9 | Blue (and other colours) |
| Emerald | Beryl (chromium) | 7.5–8 | Green |
These four are prized for their exceptional rarity, hardness (except emerald, which is softer) and enduring value.
Common Semiprecious Stones
Almost every other gemstone is classed as semiprecious — often beautiful and popular, and more affordable. Common examples include:
- Pearl (Mohs 2.5–4.5) — organic gem from the sea
- Opal (Mohs 5.5–6.5) — famous for its play of colour
- Moonstone — aluminium silicate with a soft glow
- Blue Topaz — a silicate mineral
- Black Onyx — a form of chalcedony
- …and many more, including amethyst, garnet, citrine, turquoise and coral
Precious vs Semiprecious – Quick Summary
| Precious | Semiprecious | |
|---|---|---|
| Number | Only 4 (diamond, ruby, sapphire, emerald) | Many varieties |
| Rarity | Very rare | More available |
| Hardness | Generally very hard | Varies (soft to hard) |
| Price | Higher, premium | More affordable |
Explore Gemstones at AstroKapoor
Whether you’re drawn to a precious or a semiprecious stone, AstroKapoor offers 100% natural, certified gems. Buy Certified Gemstones Online or browse our full Gems & Gemstones collection. For an astrological pick, get a Vedic gemstone recommendation.
Frequently Asked Questions
What is the difference between precious and semiprecious stones?
The difference is based mainly on rarity, hardness and value. Only four gems — diamond, ruby, sapphire and emerald — are classed as precious, while all other gemstones are semiprecious. There is no strict scientific line; the main difference is cost, rarity and durability.
Which are the four precious stones?
The four precious stones are diamond, ruby, sapphire and emerald. They are prized for their exceptional rarity, beauty and (except emerald) their hardness.
What are some common semiprecious stones?
Common semiprecious stones include pearl, opal, moonstone, blue topaz, black onyx, amethyst, garnet, citrine, turquoise and coral, among many others.
Are semiprecious stones less valuable?
Generally, semiprecious stones are more affordable than precious stones, but many are beautiful, durable and highly valued in their own right. Rare or fine-quality semiprecious stones can be very valuable.
How are gemstones classified as precious or semiprecious?
They are classified mainly by rarity, hardness (durability), value and beauty. Precious stones are rarer, harder and more expensive, while semiprecious stones are more widely available and affordable.
