Wonderstone: Banded rhyolitic tuff coloured by iron oxide staining in concentric and wavy Liesegang bands, Origins, Treatments, Prices and Uses

The facts

Species

Banded rhyolitic tuff coloured by iron oxide staining in concentric and wavy Liesegang bands

Chemistry

Rhyolitic tuff of quartz, feldspar and clay, with hematite and goethite banding

Hardness

5.5-6.5 on the Mohs scale

Refractive index

1.54 approx. (spot)

Specific gravity

2.30-2.60

Crystal system

Aggregate

Cleavage

None

Cause of colour

Iron oxide and hydroxide deposited in Liesegang diffusion bands after deposition

Origins

Vernon Hills and the Sheeprock Mountains, Tooele and Juab Counties, Utah, USA · Nevada, USA · South Africa (a different, pyrophyllite-based 'wonderstone' shares the name)

Treatment

Untreated; porous pieces are stabilised. Note the name collision: South African wonderstone is a pyrophyllite rock used for machined industrial parts and carving, a completely different material from Utah wonderstone. Utah collecting on BLM land is subject to hobby quantity limits. Not CITES.

Confused with

Picture jasper, South African pyrophyllite wonderstone, Banded sandstone, Landscape marble

Price guidance

$2-10 per kilogram rough; cabochons $5-40

What wonderstone actually is

Mineralogically, wonderstone is banded rhyolitic tuff coloured by iron oxide staining in concentric and wavy Liesegang bands — Rhyolitic tuff of quartz, feldspar and clay, with hematite and goethite banding, crystallising in the aggregate system.

The colour is caused by iron oxide and hydroxide deposited in Liesegang diffusion bands after deposition. That is worth knowing because it determines what heating, light and time can and cannot do to the stone.

A refractometer reads 1.54 approx. (spot), and the specific gravity sits near 2.30-2.60; cleavage is none.

Where wonderstone comes from

The recognised sources are Vernon Hills and the Sheeprock Mountains, Tooele and Juab Counties, Utah, USA, Nevada, USA and South Africa (a different, pyrophyllite-based 'wonderstone' shares the name).

Origin affects price in this material, so we name the locality on every quote rather than the country. "African" or "Asian" tells a buyer nothing.

How wonderstone is treated

None of this is a problem when it is said out loud. It becomes one the moment it is left out.

What wonderstone is confused with

The usual confusions are Picture jasper, South African pyrophyllite wonderstone, Banded sandstone and Landscape marble.

The separation is rarely a matter of opinion: refractive index 1.54 approx. (spot) and specific gravity 2.30-2.60 settle most of it in a minute, and magnification settles the rest.

What wonderstone is used for

Wonderstone is bought by jewellery, carving and sculpture, decorative objects and mineral collecting — and each of those trades wants a different form of the same material.

We quote each application in the unit that trade actually buys in, by the carat, by the block or by the piece.

Durability and care

Wonderstone is 5.5-6.5 on the Mohs scale, with none cleavage.

With no cleavage plane to worry about, the practical limit is abrasion rather than breakage, and it takes daily wear well.

Warm water, mild soap and a soft brush. Avoid ultrasonic cleaners on anything fracture-filled, stabilised, dyed or visibly included.

What wonderstone costs

Indicative pricing for wonderstone is $2-10 per kilogram rough; cabochons $5-40.

That is a range, not a quote. Colour, size, clarity, cut and origin move the figure a long way inside it, and the only honest price is one given against a specific stone. Send us what you need and we will price it.

Questions

Is wonderstone treated, and how?

Where does wonderstone come from?

Vernon Hills and the Sheeprock Mountains, Tooele and Juab Counties, Utah, USA, Nevada, USA and South Africa (a different, pyrophyllite-based 'wonderstone' shares the name). Origin affects price, so we name the locality rather than the country on every quote.

Is wonderstone hard enough to wear every day?

Yes. At 5.5-6.5 on the Mohs scale with no cleavage plane, it handles daily wear well. The practical limit is gradual abrasion rather than chipping.

How much does wonderstone cost?

Indicatively $2-10 per kilogram rough; cabochons $5-40. Colour, size, clarity and origin move the price a long way within that, so treat it as a range and ask for a quote against a specific stone.

What is wonderstone confused with?

Most often Picture jasper, South African pyrophyllite wonderstone, Banded sandstone and Landscape marble. A refractive index of 1.54 approx. (spot) and a specific gravity near 2.30-2.60 separate it quickly.

What is wonderstone used for besides jewellery?

carving and sculpture, decorative objects and mineral collecting. Each of those trades buys it in a different form and a different unit.

Looking for wonderstone?

Tell us the size, the quality and what it is for. We source it, photograph it and quote it — with the locality named.

Ask about wonderstone

Wonderstone