Thulite: Norway's Pink Zoisite and How to Recognize It

Short answer: thulite is the opaque pink to rose-red variety of zoisite, a calcium aluminum silicate (Ca2Al3(SiO4)3(OH)), colored by manganese. It sits around Mohs 6 to 6.5 with a specific gravity near 3.2 to 3.4, often mottled with white quartz. It was first described from Sauland in Telemark, Norway in 1823, is best known from Leksvik in Trøndelag, and is easily confused with rhodonite, which is softer and usually veined in black.

Why is thulite named after Thule?

Thule was the name classical writers gave to a land at the far north of the known world. Minerals.net explains that thulite was first found in Norway and named after this mythical region, which many identify with Norway. The Norwegian national encyclopedia, Store norske leksikon, gives the formal record: the mineral was first described from Sauland in Telemark in 1823, it is especially well known from Leksvik in Trøndelag, and some people call it Norway's national stone. That last phrasing is careful, and worth keeping careful: "some call it" is a description of popular use, not an official designation in the source.

The parent mineral is older in the literature. Minerals.net notes that zoisite was named in 1805 after Baron Sigmund Zois von Edelstein (1747 to 1819), a collector who recognized it as a distinct species, and webmineral lists Rauris and the Saualpe in Austria as its type area.

What is thulite, mineralogically?

Thulite is not a separate mineral. It is a color variety of zoisite, and Minerals.net attributes its pink to manganese in its composition. Store norske leksikon's zoisite entry describes the species as most often gray or greenish, with the red manganese-bearing variety called thulite and the clear blue variety called tanzanite. Same mineral, very different stones.

Two references give slightly different hardness and density ranges, which is normal for a massive, often quartz-rich rock rather than a clean single crystal. Webmineral's calculated values for pure zoisite (density 3.30, hardness 6.5) sit in the middle of both.

Is thulite the same as clinothulite?

Not quite, and in hand specimen you usually cannot tell. Zoisite and clinozoisite are dimorphs: same chemistry, different crystal structure, orthorhombic versus monoclinic. Geology.com notes the two are very difficult to tell apart unless crystals are well formed. The pink manganese form of clinozoisite is called clinothulite, and Minerals.net says separating it from thulite sometimes requires complex tests. Most pink "thulite" in the trade has never been through those tests, so the name describes the look as much as the proven species.

How does thulite form, and where is it found?

Zoisite is a metamorphic mineral. Geology.com describes zoisite and clinozoisite forming during regional metamorphism and hydrothermal alteration, appearing as massive material and as crystals in veins cutting schists and marbles, and in pegmatites at the edges of igneous bodies. Thulite forms where those conditions meet enough manganese to color it.

The Norwegian occurrences dominate the story:

• Sauland, Telemark: where the mineral was first described in 1823.
• Leksvik, Trøndelag: the best-known source, producing pink thulite with white quartz.
• Lom: thulite with dark red manganese-bearing epidote in quartzite. SNL's piemontite entry identifies that red mineral as piemontite and notes it is especially known with thulite from Lom and Leksvik.
• Tvedestrand, Agder: Minerals.net lists it alongside Leksvik, and pictures pink clinothulite from there.

Outside Norway, Minerals.net names the Spruce Pine district of Mitchell County, North Carolina, especially Micaville, and Geology.com adds Namibia and Australia. Geology.com also notes that thulite is rarely seen in commercial use because supply is limited and the public is unfamiliar with it, which is why most of what reaches the market is tumbles, palm stones and small spheres rather than jewelry.

What does a good piece of thulite look like?

Thulite is a dense, interlocking mass of tiny crystals, so it never shows the glassy transparency of tanzanite. Expect:

• Color: bubblegum pink to deep rose. Deeper, more even color is the more desirable look.
• White patches: Minerals.net notes thulite often occurs with quartz and is sometimes mottled with white quartz streaks or spots. That mottling is natural and part of the stone's character.
• Dark red flecks: in some Norwegian material, the deep red is piemontite, not iron staining.
• Luster: vitreous on a good polish, with pearly flashes on cleavage surfaces in rough pieces.

Does thulite glow under UV light?

Some does. Minerals.net records that thulite may fluoresce orange under longwave ultraviolet light. Webmineral lists ordinary zoisite as non-fluorescent, so a reaction is a sign of the manganese variety, though not proof. A small 365 nm flashlight is a cheap test; the fluorescence guide explains why manganese often produces orange to red glows, and the planned UV testing guide covers torches and safety.

How do you tell thulite from rhodonite and other pink stones?

Rhodonite is the usual mix-up, and the two tests that separate them are easy.

The rhodonite figures come from Minerals.net's rhodonite page. The Minerals.net thulite entry sums up the visual rule: thulite is most similar to rhodonite but usually lacks rhodonite's black streaks, lacks the banding of rhodochrosite, and is harder than rhodochrosite. Rose quartz is translucent and has no cleavage. Pink dyed stones show color pooled in cracks. If a pink stone shows heavy black lacework, it is almost certainly rhodonite.

What is "piemontite quartzite," and why is it sold as thulite?

This is the newer confusion, and it comes straight from the Norwegian deposits. The German gem lab EPI (Institut für Edelstein Prüfung) describes the Lom deposit as a manganese-rich layer of roughly 3 by 250 meters in paragneiss, and reports that mining has reached its margins, so little fresh high-quality thulite reaches the market. In its place, a neighboring rock is increasingly sold under the same name: a piemontite-muscovite quartzite, mottled wine red and often glittery from mica flakes, sometimes offered as "red aventurine quartz."

EPI's practical separation uses density. Thulite rock (thulitite) usually measures between 3.0 and 3.5, rhodonite above 3.5, and piemontite quartzite below 3.0. Blood-red speckles in a pale quartz host and a glittering surface point to piemontite quartzite rather than thulite.

Is thulite treated?

Minerals.net states that thulite is not treated or enhanced, and that the non-tanzanite forms of zoisite are naturally colored. That contrasts with its famous sibling: the same source notes tanzanite is heated to achieve its blue. Dyed pink material does exist in the bead trade for other stones, so very uniform, saturated pink with color concentrated in fractures is worth questioning.

What is thulite associated with in crystal traditions?

In crystal traditions thulite is associated with warmth, enthusiasm and self-expression, largely because of its color. These are customs attached to the stone, not measurable properties.

Shopping for thulite and zoisite we stock

Thulite is an inexpensive stone, so the main buying questions are identity and appearance rather than price.

1. Check the pattern. White quartz mottling fits thulite; dense black veining points to rhodonite.
2. Try a UV torch. An orange longwave response supports thulite, though not every piece reacts.
3. Weigh it if you can. A noticeably heavy pink stone of the same size leans toward rhodonite's higher density.
4. Ask for the locality. Norway, North Carolina, Namibia and Australia are the documented sources; a seller who knows is a good sign.

• Thulite: offered as a 2.5 inch palm stone, tumbles and a 35 mm sphere; the palm stone gives the largest polished face for judging color and quartz mottling.
• Ruby Zoisite: the green zoisite variety with ruby, in tumbles and 3.25 to 3.75 inch towers; a useful side-by-side to see how different the same mineral species can look.
• Ruby Zoisite Sphere: 36.5 to 37.5 mm spheres, close in size to the thulite sphere for a direct comparison.
• Rhodonite (Peru): Peruvian rhodonite, the stone thulite is most often mistaken for; compare the black veining.
• Rhodonite Sphere: a polished rhodonite sphere for a density check against a thulite sphere of similar size.

Frequently asked questions

Is thulite the same as pink zoisite?

Yes. Thulite is the trade and mineralogical variety name for pink to rose-red zoisite colored by manganese. Some pink material may actually be clinothulite, the monoclinic twin, which looks almost identical and can only be separated with laboratory tests.

Where does thulite come from?

It was first described from Sauland in Telemark, Norway in 1823 and is best known from Leksvik in Trøndelag. Lom produces thulite with red piemontite. Other sources include the Spruce Pine district of North Carolina, Namibia and Australia.

Is thulite Norway's national stone?

Store norske leksikon says that some people call thulite Norway's national stone. The wording describes popular use rather than an official title, so treat claims of formal national status with caution unless a seller can point to a source.

How hard is thulite?

About 6 to 6.5 on the Mohs scale according to Minerals.net, with Store norske leksikon giving 6.5 to 7. It resists a steel knife reasonably well but has one perfect cleavage, so a hard knock can split a thin palm stone or bead.

How do you tell thulite from rhodonite?

Look at the pattern and feel the weight. Rhodonite usually carries black manganese oxide veins and is denser (3.4 to 3.7). Thulite tends to be pink with white quartz patches and sits around 3.2 to 3.4. An orange glow under longwave UV also points to thulite.

Sources

• Store norske leksikon, Thulitt: https://snl.no/thulitt
• Store norske leksikon, Zoisitt: https://snl.no/zoisitt
• Store norske leksikon, Piemontitt: https://snl.no/piemontitt
• Minerals.net, Thulite (gemstone): https://www.minerals.net/gemstone/thulite_gemstone.aspx
• Minerals.net, Zoisite: https://www.minerals.net/mineral/zoisite.aspx
• Minerals.net, Zoisite (gemstone): https://www.minerals.net/gemstone/zoisite_gemstone.aspx
• Minerals.net, Rhodonite: https://www.minerals.net/mineral/rhodonite.aspx
• Institut für Edelstein Prüfung (EPI), Mn-Zoisite (Thulite), Piemontite-Quartzite and Rhodonite: https://epigem.de/en-us/informations/lookalikes/thulitite-piemontite-quartzite.html
• Geology.com, Zoisite and Clinozoisite: https://geology.com/minerals/zoisite.shtml
• Webmineral, Zoisite Mineral Data: http://webmineral.com/data/Zoisite.shtml