Citrine
Natural citrine is genuinely uncommon. Most of what is sold as citrine started life as amethyst and was heated until it changed colour. This is the single most useful fact about the stone.
Is citrine natural or heat-treated?
Amethyst and citrine are the same mineral — quartz — coloured by iron in different oxidation states. Heat amethyst to a few hundred degrees and the iron changes state, and the purple turns yellow to orange. Some of this happens in the earth. Most of it happens in Brazil, deliberately.
Heat-treated citrine is still citrine: real quartz, permanently coloured, stable for life. It is not glass, not dyed, not synthetic. But it should be disclosed, and the price should reflect it.
How can you tell natural from heat-treated citrine?
Heat-treated material tends toward a reddish or burnt orange, often with a slightly cloudy or milky base, and frequently shows colour concentrated at the crystal tips with a pale zone below. Natural citrine leans a softer, cooler lemon to golden yellow with more even distribution.
Two names worth knowing. Madeira citrine is a deep reddish-orange, almost always heated. Anything sold as a vivid, saturated orange for very little money is heated, and that is fine — it just isn't rare.
What should you look for in citrine?
Even colour across the face, and no washed-out corners. Citrine is usually clean to the eye, so visible inclusions are a reason to move on rather than a fact of the stone. Cut matters: quartz has modest refractive index, so a shallow, hurried cut goes lifeless and windowed. Look through the table at a printed page — if you can read it, the stone is cut too shallow.
Is citrine durable enough for daily wear?
Mohs 7. One of the best value hard stones for daily wear. Tough, stable, and not prone to cleavage.
How do you care for citrine?
Warm soapy water and a soft brush. Keep it out of prolonged direct sunlight and away from steam — the same heat that made the colour can shift it further. Ultrasonic is generally safe on clean stones.
Why is citrine a November birthstone?
November's birthstone alongside topaz, and the one that carries the long association with warmth, generosity and — inevitably, given the colour — money.