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Yellow Crystal Identification: How to Name a Yellow Stone

By Digital Towns Crystals ยท Last reviewed October 8, 2026

Short answer: first decide whether the stone shines like metal. A brassy metallic yellow is almost always pyrite, sometimes chalcopyrite, and a streak test separates both from gold. A glassy or resinous yellow is usually citrine, calcite, fluorite or sulfur, with orpiment and wulfenite as collector pieces. Hardness then does most of the work: citrine scratches glass, fluorite and calcite do not, and sulfur can be marked with a fingernail.

Yellow divides more cleanly than any other color, and the dividing line is luster. One group reflects light like polished brass and is opaque even in thin edges. The other lets light in, from the water-clear yellow of a citrine point to the waxy glow of a sulfur crystal. Get that first call right and the remaining candidates are few. The color causes guide explains where each yellow comes from chemically; this page sticks to the bench tests.

Does your yellow stone look like metal?

If it does, the shortlist is pyrite, chalcopyrite, marcasite and, rarely, native gold. Geology.com describes pyrite as having a brass-yellow color, a metallic luster and a high specific gravity, noting that it is harder than other yellow metallic minerals and often forms cubes, octahedrons or pyritohedrons with striated faces. Minerals.net lists its hardness at 6 to 6.5 and specific gravity at 4.9 to 5.2.

The decisive test is streak. Rub a corner across the back of an unglazed tile. Pyrite leaves a greenish black powder. Gold leaves yellow. Geology.com adds a second check: gold is very soft and will bend or dent with pin pressure, while pyrite is brittle and thin pieces break. Chalcopyrite is the other common brassy mineral; Minerals.net describes it as lower hardness than pyrite with a more intense yellow color. The hematite vs pyrite comparison covers the other metallic look-alike buyers meet.

Which non-metallic yellow minerals are you likely holding?

Candidate Composition Mohs SG Streak Field clue
Citrine Quartz, SiO2 7 2.6 to 2.7 White Scratches glass; six-sided points
Yellow calcite CaCO3 3 2.7 White Rhomb-shaped breaks; soft
Yellow fluorite CaF2 4 3.0 to 3.3 White Cubes; often fluoresces
Sulfur S 1.5 to 2.5 2.0 to 2.1 Pale Very light; resinous; cracks when warmed
Orpiment As2S3 1.5 to 2 3.4 to 3.5 Yellow Flexible flakes; with red realgar
Wulfenite PbMoO4 3 6.5 to 7 White Square plates; very heavy

The table shows how far apart these stones sit even though they can share a color. Sulfur and wulfenite are both soft, but a wulfenite plate weighs more than three times as much as a sulfur crystal of the same size. Citrine is the only one hard enough to scratch glass reliably.

Sulfur

Sulfur gives itself away by weight. Minerals.net puts its specific gravity at 2.0 to 2.1, lighter than any other common yellow mineral, and its hardness at 1.5 to 2.5. Crystals have an adamantine shine on clean faces and a resinous one elsewhere. Geology.com lists its diagnostic properties as yellow color, low hardness, low specific gravity, extreme flammability with a blue flame, and a low melting temperature. Do not test that last property.

Fluorite and calcite

Both are soft and both come in honey to lemon yellows, but their shapes differ. Fluorite grows as cubes and breaks with perfect cleavage, and Minerals.net gives it a hardness of 4 and specific gravity of 3.0 to 3.3. Calcite has hardness 3, breaks into slanted rhombs and fizzes in dilute acid. Minerals.net lists yellow among the many colors calcite takes, and golden "honey" calcite is a common tumbled and carved stone. The fluorite vs calcite comparison goes through the full set of differences.

Orpiment

Orpiment is the arsenic sulfide often found with red realgar. Minerals.net explains that its name comes from the Latin Auripigmentum, meaning gold pigment, from its historical use as a yellow pigment. It has a yellow streak, a resinous to pearly luster, and thin flakes that bend. Treat it as a cabinet specimen: handle it with care and wash hands afterward.

Is your yellow quartz natural citrine or heated amethyst?

This is the most common question about yellow stones, and the honest answer is usually "heated". GIA states that natural citrine is rare and that most citrine on the market is the result of heat treatment of amethyst. GIA also attributes citrine's yellow-to-orange color to a trace of iron in the structure.

The heat sets the shade. Minerals.net reports that heating amethyst at about 750 degrees Fahrenheit will produce a mild yellow color, and that heating to about 1700 degrees produces deep orange to reddish colors; it adds that most heat treated citrine has a reddish tint. That is why deep orange shades and burnt-orange tips on cheap citrine clusters are a strong hint of treatment. Geology.com describes how large geodes are discovered full of purple amethyst and then heated in industrial ovens to convert the crystals to orangy brown citrine.

The quick visual check on a cluster: heated amethyst often shows white or milky bases rising to dark orange tips, because the color followed the original amethyst zoning. Natural citrine tends to be a paler, more even smoky yellow throughout. The natural vs heated citrine guide has more detail and photos to compare. Lemon-colored quartz sold as "lemon quartz" or "lemon citrine" deserves the same questions about how the color was produced, and the dyed quartz guide covers dyed yellow quartz.

Which yellow minerals change over time?

Three in this color group need care. Sulfur is the most fragile: Minerals.net warns that it can crack when exposed to mild heat, including body heat, that it should be handled as little as possible, and that it should not be washed. A sulfur crystal carried in a warm pocket or held under a hot display lamp can fracture. Orpiment is photosensitive and, like realgar, should be stored away from light. Pyrite can tarnish; Minerals.net notes that some specimens develop a yellow-brown film on crystal faces, and humidity drives the worse problem of pyrite decay, covered in the pyrite decay guide.

Citrine, by contrast, is stable in normal room light, and calcite and fluorite keep their yellow under ordinary display conditions.

Shopping the yellow crystals we stock

For yellow quartz, ask whether the color is natural or heat-produced; a good seller will say. For pyrite, ask about storage, and check photos for dull or powdery patches that signal decay. For soft specimens, look for sharp, undamaged edges and corners, since calcite and fluorite chip easily in transit.

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Frequently asked questions

How do I tell pyrite from gold?

Do a streak test on an unglazed tile. Pyrite leaves a greenish black streak, gold a yellow one. Gold is also soft enough to dent with a pin, while pyrite is hard and brittle and will chip. Pyrite usually forms sharp cubes or striated crystals; gold rarely does.

Is most citrine fake?

Most citrine is real quartz, but most of it gets its color from heating amethyst rather than from nature. GIA calls natural citrine rare. Heated citrine is a genuine mineral with a treated color, and it should be sold with that disclosed. Glass and dyed quartz sold as citrine are the actual fakes.

Why is my sulfur crystal cracking?

Sulfur is soft and brittle and tends to crack with mild heat, even body heat, so the warmth of a hand, a sunny window or a display lamp can be enough. Keep it in a closed box at stable room temperature, handle it rarely and never wash it in warm water.

What is honey calcite?

It is ordinary calcite with a golden to amber color. It has hardness 3, breaks into rhomb-shaped pieces and fizzes in dilute acid. It is sold tumbled, carved and as rough chunks, and it scratches easily, so store it apart from harder stones such as citrine.

Is yellow fluorite rare?

Yellow fluorite is less common than purple or green but is not rare. Small Moroccan clusters of yellow cubes sell at modest prices. Cleaner, larger and more transparent cubes cost more, and any fluorite needs careful packing because it cleaves easily.

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