The facts
What oligoclase actually is
The species behind oligoclase is feldspar group (plagioclase), (Na,Ca)(Si,Al)₄O₈, An₁₀–An₃₀; it forms in the triclinic system.
Colourless when pure; hematite and goethite platelets give aventurescence, lamellar twinning gives schiller is responsible for the colour — and the chromophore, not the name, is what decides whether a colour is stable.
On the instruments it reads a refractive index of 1.538–1.550 and a specific gravity of about 2.62–2.67, with perfect basal, good prismatic cleavage.
Where oligoclase comes from
Commercial material comes from Tvedestrand, Aust-Agder, Norway, Ytterby, Sweden and Mysore, Karnataka, India.
Different localities give different colour and different clarity, and the trade prices them differently. We state which one.
How oligoclase is treated
Generally untreated. Some Indian sunstone-oligoclase is backed or impregnated to stabilise thin cabochons.
We state the treatment on every stone, including when the honest answer is that it cannot be determined. A treatment disclosed is a fact; a treatment discovered later is a refund.
What oligoclase is confused with
Watch for Albite, Andesine, Labradorite and Moonstone — these are what turn up sold under this name.
The separation is rarely a matter of opinion: refractive index 1.538–1.550 and specific gravity 2.62–2.67 settle most of it in a minute, and magnification settles the rest.
What oligoclase is used for
The trades that buy oligoclase are jewellery, mineral collecting and architecture and interiors. They do not want the same thing, and they do not pay in the same unit.
We quote each application in the unit that trade actually buys in, by the carat, by the specimen or by the square metre.
Durability and care
Oligoclase is 6–6.5 on the Mohs scale, with perfect basal, good prismatic cleavage.
Hardness is not the whole story. Perfect cleavage means the stone can split cleanly if struck along the wrong plane, whatever its Mohs number, so a protective setting matters more here than the hardness suggests.
Warm water, mild soap and a soft brush. Avoid ultrasonic cleaners on anything fracture-filled, stabilised, dyed or visibly included.
What oligoclase costs
Expect roughly 2–25 USD/ct for clean faceted material, depending on quality.
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 oligoclase treated, and how?
Generally untreated. Some Indian sunstone-oligoclase is backed or impregnated to stabilise thin cabochons.
Where does oligoclase come from?
Tvedestrand, Aust-Agder, Norway, Ytterby, Sweden and Mysore, Karnataka, India. Origin affects price, so we name the locality rather than the country on every quote.
Is oligoclase hard enough to wear every day?
With care. It is 6–6.5 on the Mohs scale, which is hard enough, but perfect basal, good prismatic cleavage means it can split if struck at the wrong angle. Use a protective setting and avoid ultrasonic cleaning.
How much does oligoclase cost?
Indicatively 2–25 USD/ct for clean faceted material. 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 oligoclase confused with?
Most often Albite, Andesine, Labradorite and Moonstone. A refractive index of 1.538–1.550 and a specific gravity near 2.62–2.67 separate it quickly.
What is oligoclase used for besides jewellery?
mineral collecting and architecture and interiors. Each of those trades buys it in a different form and a different unit.
Related stones
Looking for oligoclase?
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 oligoclase