Opal: A Buyer's Guide
Opal is the only gemstone that cannot be graded against a standard, because no two are alike. It is also the most fragile thing we sell, and the two facts are related.
What opal actually is
Opal is not a crystal. It is hydrated silica — microscopic spheres of silicon dioxide packed together, with water making up between three and ten percent of the stone by weight.
Where those spheres are uniform in size and stacked in a regular three-dimensional array, they diffract light like a natural photonic crystal. That is play-of-colour: not pigment, not refraction, but light interference. Sphere diameter determines which colours appear. Small spheres produce blue and violet; larger ones produce orange and red, which is why red is the rarest and most sought.
Because the arrangement forms by accident of deposition, every opal's pattern is genuinely unrepeatable. You are not buying a grade. You are buying one specific object.
Types
| Type | Description | Main source |
|---|---|---|
| Black opal | Play-of-colour against a dark body tone. The most prized | Lightning Ridge, Australia |
| Boulder opal | Opal in seams within ironstone; the host rock is left attached | Queensland, Australia |
| Crystal opal | Transparent to semi-transparent with play-of-colour throughout | Australia, Ethiopia |
| White / milky opal | Light body tone; softer, more pastel play-of-colour | Coober Pedy, Australia |
| Fire opal | Orange to red body colour, often without play-of-colour | Mexico |
| Welo opal | Ethiopian; bright play-of-colour, often in a honeycomb pattern | Wollo Province, Ethiopia |
Ethiopian Welo — what you need to know
Welo opal arrived on the market in 2008 and changed the category. It offers strong, bright play-of-colour at a level far more people can reach, and it is a genuinely lovely material.
It is also hydrophane, which Australian opal is not. Hydrophane opal is porous: it absorbs water. A Welo opal submerged in water will become temporarily transparent and lose its play-of-colour entirely, recovering over hours or days as it dries.
This matters practically. A Welo opal ring worn while washing hands repeatedly can cloud. It can also absorb oils, soaps and dyes permanently, which discolours it. Some Welo is smoke-treated or sugar-treated to darken the body tone and imitate black opal, and hydrophane opal accepts such treatments readily. None of this makes Welo a bad buy — it makes it a stone you need to be told about honestly, and most sellers do not mention it at all.
What determines value
Body tone
Graded on a scale from N1 (black) to N9 (white). Darker body tone makes play-of-colour read more vividly, which is why black opal sits at the top.
Brightness
Often the single most important factor. A brilliant stone with a simple pattern generally outranks a dull one with a complex pattern.
Colour range
Red is rarest, then orange, then green, then blue. A stone showing the full spectrum outranks one showing only blue-green. Red-on-black is the summit of the category.
Pattern
Named patterns carry premiums — harlequin (regular angular patches) is the most sought and genuinely rare. Others include pinfire, flagstone, ribbon and rolling flash.
Directionality
Some opals only show their play-of-colour from certain angles. A stone that fires from all directions is worth considerably more than one with a single good face.
Durability — the honest position
Mohs 5.5–6.5, with water content. This is the softest and most vulnerable material we handle.
Opal scratches easily — household dust at Mohs 7 will mark it. It is sensitive to knocks, and it can craze: develop a network of fine internal cracks, usually from drying out or thermal shock. Crazing is permanent and cannot be repaired.
| Use | Suitability |
|---|---|
| Pendants, earrings, brooches | Excellent. Protected and rarely struck |
| Occasional-wear rings, bezel set | Acceptable with care |
| Daily engagement ring | We advise against it |
| Ultrasonic or steam cleaning | Never |
We will say this to anyone who asks: an opal engagement ring is a stone you will eventually damage. Beautiful for a few years, then chipped or crazed. If you want that iridescence in a ring worn every day, we would rather talk to you about it than take the order and stay quiet.
Setting and caring for opal
Bezel settings are the sensible choice — they protect the girdle and edges where damage starts. Avoid prongs that grip the stone tightly; opal does not tolerate pressure.
Care rules: warm water and a soft cloth only. Never ultrasonic, never steam. Avoid sudden temperature change, dry heat and very low humidity. Remove before swimming, washing up or applying cosmetics. For Welo specifically, remove before any contact with water at all.
Do not store opal in a bank vault or a sealed dry container for years. The water content matters and prolonged dry storage is a known cause of crazing.
How we source opal
Because every opal is unique, sourcing is a matter of showing you actual stones rather than matching a specification. Tell us the type, rough size and budget bracket, and whether Australian or Ethiopian.
Every candidate is filmed rotating under moving light, since directionality is a real value factor and a still image tells you nothing about whether a stone fires from every angle. We disclose hydrophane status and any treatment on every stone, without being asked.
Turnaround is two to four weeks. Fine Australian black opal takes longer.
Frequently asked questions
Can I wear an opal engagement ring?
We advise against it. At Mohs 5.5–6.5 with water content, opal scratches from household dust, chips from knocks, and can craze permanently from drying or thermal shock. An opal in a daily ring is a stone you will eventually damage. For pendants and earrings it is a wonderful choice; for a ring worn every day it is not.
What is hydrophane opal and does it matter?
Hydrophane opal is porous and absorbs water — most Ethiopian Welo opal is hydrophane, Australian opal is not. A Welo opal submerged in water becomes temporarily transparent and loses its play-of-colour, recovering as it dries. It can also permanently absorb oils, soaps and dyes. It matters enough that you should be told before buying, and we always disclose it.
Why is black opal the most valuable?
Body tone. A dark background makes play-of-colour read far more vividly than a light one does, the same way a colour looks more intense against black than against white. Lightning Ridge in Australia is the main source. Combined with red flash, which is the rarest colour, black opal is the summit of the category.
What is crazing and can it be fixed?
Crazing is a network of fine internal cracks that develops in opal, usually from drying out or thermal shock. It is permanent and cannot be repaired or polished away. Prevention is the only option: avoid sudden temperature change, very low humidity, dry heat, and prolonged storage in a sealed dry container.
How do I clean an opal?
Warm water and a soft cloth only. Never ultrasonic and never steam — both can craze the stone or damage a doublet or triplet. Avoid soaps and detergents, particularly on hydrophane material, which absorbs them permanently. Remove opal jewellery before swimming, washing up, or applying cosmetics and perfume.
What is a doublet or triplet?
Assembled stones. A doublet is a thin slice of natural opal bonded to a dark backing to imitate black opal. A triplet adds a clear quartz or glass cap over the top. Both are legitimate products when disclosed, and both cost far less than solid opal. They are also more vulnerable to water, which can separate the layers. We disclose construction on every stone.
Australian or Ethiopian opal?
Australian opal is not hydrophane, is generally more stable, and includes the finest black opal in the world. Ethiopian Welo offers brighter play-of-colour at a level far more people can reach, but is porous and needs more care. Neither is better in the abstract — it depends on how the stone will be worn and what you want to spend.
Do you ship opal internationally?
Yes, worldwide, with insured tracked courier and full customs documentation. Because every opal is unique and directionality matters, we film each candidate rotating under moving light — a still image tells you nothing about whether a stone fires from every angle.
Enquire About an Opal
Tell us the type and rough size you want. We will show you actual stones on video, rotating under moving light, with hydrophane status and any treatment disclosed.
Tinch Jewels · Borivali West, Mumbai 400092, India · Worldwide insured shipping
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