Blue Opal from Peru, hand-graded by The Stone Atlas, lot XA4
Origin Ica, Peru
Mohs hardness 56.5 / 10
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Fingernail (2.5) Steel knife (5.5) Diamond (10)

Stone properties

What this stone is, geologically

Crystal system
Amorphous
Mohs hardness
5 – 6.5
Specific gravity
1.98–2.25
Refractive index
1.37–1.47
Transparency
Transparent to opaque
Durability
Moderate — protect from impact and dehydration

Hydrated silica spheres arranged in lattices that diffract light. Forms slowly at the surface from silica-rich groundwater.

The lot

Full description

A hand-graded parcel of cabochons of blue opal from Ica, Peru, calibrated to the 18 mm working range. Sold by the parcel, weighed in carats, treatments disclosed.

About this lot

Origin: Ica, Peru.

Parcel: Minimum guaranteed 10 ct total weight. Each parcel typically contains 1–2 pieces within the listed size range. You pay for guaranteed weight; piece count varies because natural material isn't uniform.

Size: 18 mm.

Weight: Minimum 10 ct per parcel (parent lot has 429 ct available).

Treatment: None. 100% natural, untreated material. Disclosed on every listing — that's the Atlas standard.

Suggested use

Premium jewellery settings — bezel mounts in 14k or 18k gold, sterling silver collector pieces. Treat with care: not impact-resistant.

The Stone Atlas standard

Hand-graded in our US studio. Treatments disclosed on every listing, no exceptions. Shipped insured from the US since 1995. Returns within 14 days if the stone in hand doesn't match the listing.

Shipping & returns

  • Ships: from the US within 1–2 business days.
  • Insurance: tracked, insured for full declared value, no signature required under $1,000.
  • Returns: 30 days from delivery if the stone in hand doesn't match the listing — we cover return shipping.

Common questions

About this stone.

Is this stone treated?

No. This Blue Opal is 100% natural with no heat, diffusion, dyeing, or fracture-filling treatment. We disclose treatment on every listing without exception — when it says "untreated," it is.

Where is this stone from?

This piece is from Ica, Peru.When we know the specific city or mine, we tag it on every listing. When the supplier chain is generalized, we mark it "most likely from" rather than fabricate a precise origin.

Can I see a GIA certificate?

Yes. GIA certification is available as a $95 add-on after checkout. Request it once your order ships — we'll send the stone to GIA on your behalf and forward the certificate when it arrives (typically 3–4 weeks).

What's your return policy?

Every stone comes with a 30-day inspection window. If the stone doesn't match the listing or you simply don't love it, return it within 30 days of delivery for a full refund. We cover return shipping. No restocking fees, no questions.

How long does shipping take?

Orders ship from the US within 1–2 business days. Domestic US delivery is typically 2–5 business days via USPS Priority or UPS Ground, tracked end-to-end and insured for the full declared value. International shipping is available at checkout.

Is the size in the listing exact?

Listed size for this piece: 18 mm. Listed weight: 10 ct ct. All sizes and weights are hand-measured. If a stone arrives outside the listed tolerance, return it within 30 days for a full refund.

Can I see this stone in different lighting before I buy?

Yes. Use the "Ask the Atlas desk" button on this page to request additional photos under daylight, lamp light, or any specific condition. We typically reply within one business day with photos attached.

What if I'm a jeweler — do you offer wholesale?

For working jewelers and lapidary studios placing recurring orders, contact us through the Atlas desk to discuss volume pricing. For one-off custom commissions, the listed prices already reflect hand-graded quality at a fair retail tier.

4.8 out of 5

27 verified buyers

What buyers say

  1. Sofia

    Amsterdam Netherlands

    Verified buyer 157d ago

    Real natural inclusions, just like the listing said

  2. Priya

    Sydney Australia

    Verified buyer 162d ago

    Compared this to two others I bought from competitors. Clearly better saturation. Stone Atlas is now my go-to

  3. Layla

    Boulder CO

    Verified buyer 2d ago

    Tracking notifications were perfect. Always knew where my order was

  4. Emma

    Lexington KY

    Verified buyer 7d ago

    Used this for a lapidary class — perfect for what we needed

  5. Lucas

    Florence Italy

    Verified buyer 12d ago

    Beautiful stone. Treatment was disclosed up front, exactly as the listing said. That kind of honesty is rare in this trade

  6. Ruth

    Taipei Taiwan

    Verified buyer 17d ago

    Photos don't do this justice. Even better in hand

  7. Klara

    Asheville NC

    Verified buyer 22d ago

    Beautiful. Will order again

  8. Jun

    Park City UT

    Verified buyer 27d ago

    Stone is exactly the size and weight described

  9. Renata

    Munich Germany

    Verified buyer 32d ago

    Beautiful color in natural light. Lamp light brings out a different character

  10. Zola

    Kyoto Japan

    Verified buyer 37d ago

    Arrived faster than expected, tracked the whole way. The kraft box with the wax seal is a beautiful touch

  11. Isabella

    Marrakech Morocco

    Verified buyer 42d ago

    Atlas standard is real. Treatment honesty matters

  12. Jonas

    Bend OR

    Verified buyer 47d ago

    Set this into a pendant for my partner. They love it

  13. Ines

    Paris France

    Verified buyer 52d ago

    Beautiful piece. Couldn't be happier

  14. Yuki

    Helsinki Finland

    Verified buyer 57d ago

    The shipping was insured and tracked end-to-end. Felt safe ordering

  15. Mateo

    São Paulo Brazil

    Verified buyer 62d ago

    Bought this for a custom ring setting. The depth of color is gorgeous and the size is perfect

  16. Tinashe

    Taos NM

    Verified buyer 67d ago

    Will be back for more. Quality is consistent

  17. Noah

    London UK

    Verified buyer 72d ago

    My third order from the Atlas. Consistency is excellent

  18. Abigail

    Brussels Belgium

    Verified buyer 77d ago

    Worth every dollar. Real natural stone, no funny business

  19. Henrik

    Melbourne Australia

    Verified buyer 82d ago

    Origin was tagged to the city. Appreciate that level of provenance detail

  20. Matteo

    Madison WI

    Verified buyer 87d ago

    I've ordered from a lot of online gemstone dealers — this is the first time the stone matched the listing photo

  21. Rohan

    Portland ME

    Verified buyer 92d ago

    Highly recommend

  22. Nour

    Barcelona Spain

    Verified buyer 97d ago

    Smaller than I imagined but quality is high — exactly as listed

  23. Mia

    Mumbai India

    Verified buyer 102d ago

    Fast shipping, beautiful packaging, accurate listing. What more can you ask

  24. Owen

    Bozeman MT

    Verified buyer 107d ago

    Bought as a 10-year anniversary gift. Stunning

  25. Iris

    Jackson WY

    Verified buyer 112d ago

    The 30-day inspection window made me comfortable ordering at this price point. Didn't need to use it

  26. Niels

    Vienna Austria

    Verified buyer 117d ago

    Exactly what I needed for my project

  27. Arjun

    Seoul Korea

    Verified buyer 122d ago

    Working on a custom necklace; this is the centerpiece