Short answer: hemimorphite is a hydrous zinc silicate, Zn4Si2O7(OH)2·H2O, formed where zinc ore weathers near the surface. Collectors know it in two looks that seem unrelated: glossy blue botryoidal crusts, mostly from Yunnan, China, and colorless to white bladed crystals and fans, classically from Mexico. It is Mohs 4.5 to 5 with SG 3.4 to 3.5, and it is often confused with smithsonite and chrysocolla.
Why does hemimorphite come in two such different forms?
Minerals.net puts it bluntly: hemimorphite has two main patterns, a well-crystallized form and a microcrystalline globular form, and they look so different that it is surprising they are the same mineral (Minerals.net). The difference is growth speed and space. Slow growth into an open cavity makes thin, flat blades and fan-shaped sprays. Many tiny crystals growing outward together from the cavity wall make rounded, bubbly botryoidal masses, the "blue grape" crusts that dominate the decorative market.
The name describes the crystals, not the bubbles. Hemi means half and morph means form, because a hemimorphite crystal has differently shaped terminations at each end of its main axis (IGS). In most specimens one end is buried in matrix, so the asymmetry is hard to see without a loose, doubly terminated crystal. The same lopsided structure makes it pyroelectric: warm a crystal and it develops an electrical charge.
| Property | Hemimorphite |
|---|---|
| Formula | Zn4Si2O7(OH)2·H2O |
| Zinc content | 54.29% by weight (calculated) |
| Crystal system | Orthorhombic |
| Mohs hardness | 4.5 to 5 |
| Specific gravity | 3.4 to 3.5 |
| Cleavage | Perfect in one direction; brittle |
| Luster | Vitreous to adamantine on crystals; silky, waxy or dull on globular forms |
| Fluorescence | Weak bluish in shortwave UV; some pale orange in longwave |
Webmineral's calculated composition gives zinc at 54.29% of the weight (webmineral), which is why hemimorphite has been mined as a minor zinc ore.
How does hemimorphite form?
Hemimorphite is a secondary mineral. Geology.com explains that most of it forms in the rocks above and around zinc deposits, where primary zinc ore such as sphalerite weathers and the released zinc combines with silica (Geology.com). Some forms where zinc-bearing rocks undergo metasomatism. It can replace sulfides as crusts, coat fractures and cavities, or fill cavities as granular masses. The best specimens are often the last crystals to form, growing unobstructed into a cavity.
That puts hemimorphite in the same weathered upper zone as smithsonite, cerussite, anglesite and galena remnants, and in mixed lead-zinc-copper deposits it shares shelf space with aurichalcite, rosasite, mimetite and wulfenite. The oxidation zone guide covers the chemistry of that setting, the same one that grows azurite in copper deposits.
Mexico or China: where does blue hemimorphite come from?
Color is mostly a locality signal. Most hemimorphite worldwide is white, gray, colorless or brown, and Geology.com describes yellow, bluish green and bright blue specimens as rare.
| Locality | What it produces |
|---|---|
| Wenshan and Dulong, Yunnan, China | Deep neon to electric blue botryoidal crusts |
| Ojuela Mine, Mapimí, Durango, Mexico | Well-shaped crystals and fans on limonite |
| Santa Eulalia, Chihuahua, Mexico | Very large white crystals and fans |
| Santo Niño Mine, Durango, Mexico | "Toothpaste blue" botryoidal material |
| 79 Mine, Gila County, Arizona | Pale blue and greenish rounded aggregates |
| Sterling Hill, New Jersey | Rounded white aggregates and drusy crystals |
| Skorpion Mine, Namibia | Pale blue spiky crystals |
Minerals.net calls Mexico probably the most prolific country for collectible hemimorphite specimens, and names Dulong and Wenshan as the source of China's outstanding neon blue globular material. In practice, a saturated electric blue bubbly plate is almost always Chinese, a colorless fan of blades on rusty limonite is usually Ojuela, and pale sky-blue crusts can be Mexican, Arizonan or African. The regional guides to Mexico and China place these mines in context.
What was calamine, and how do you tell hemimorphite from smithsonite?
For centuries hemimorphite and smithsonite (zinc carbonate) were treated as one zinc ore called calamine. Minerals.net credits the British mineralogist James Smithson with showing in 1803 that they were two distinct species. Adolph Kenngott proposed the name hemimorphite in 1853, and Geology.com reports that the International Mineralogical Association adopted it in 1962.
They still get mixed up, partly because they often grow intergrown in a single specimen. Three checks separate pure pieces:
- Weight. Hemimorphite's specific gravity is 3.4 to 3.5; smithsonite's is 4.3 to 4.5 (Geology.com, Smithsonite). A smithsonite crust feels distinctly heavier.
- Acid. Smithsonite effervesces in cold, dilute hydrochloric acid; hemimorphite does not. This is a destructive test for rough material only, never a finished piece.
- Cleavage. Hemimorphite has one perfect cleavage; smithsonite has two that meet at rhombic angles.
A mixed specimen gives an intermediate weight and a weak fizz, which is itself a useful answer.
What else gets mistaken for blue hemimorphite?
The IGS lists smithsonite, chrysocolla and turquoise as natural lookalikes, all with clearly different specific gravities, and partially devitrified glass as an artificial simulant. There are no known synthetic hemimorphites. The most striking case went the other way: Geology.com reports that GIA's lab received a translucent electric blue cabochon of 5.61 carats submitted for a Paraíba tourmaline origin report, and testing showed it was hemimorphite with a Paraíba-like color.
Dyeing is the other risk with blue botryoidal minerals generally. Natural Chinese hemimorphite has color that runs evenly through the bubbles and shades subtly between them; paint or dye tends to pool in crevices or sit as a flat film.
Is hemimorphite good for jewelry?
It is a collector's gem rather than an everyday one. At 4.5 to 5 with perfect cleavage it scratches and breaks easily, so Geology.com suggests earrings, pins and pendants over rings and bracelets. Faceted hemimorphite is very rare; the IGS says only Mexico has produced suitable material so far, with transparent Mapimí and Santa Eulalia crystals that may yield stones up to approximately 7 to 10 carats. Blue cabochons are cut from massive material from many sources.
How should you care for hemimorphite?
Store it where nothing harder rubs against it, and clean it only with a soft brush, mild detergent and warm water, as the IGS recommends. Botryoidal crusts have deep crevices that trap dust; a soft makeup brush or a gentle puff of air works better than a cloth. Avoid ultrasonic cleaners and acids. Hemimorphite is a zinc mineral; normal handling of a stable specimen is fine, and washing your hands afterwards is good practice with any raw ore-zone material.
In crystal traditions, blue hemimorphite is associated with communication and calm. That is a belief, not a property of the mineral.
Buying blue hemimorphite: what to look for
Large, bright Chinese plates are the most expensive form, and price rises with color intensity, coverage and the size of the bubbles.
- Color. Electric blue to deep turquoise blue, consistent across the piece, is the top grade. Pale, chalky or patchy color is lower.
- Luster. Fresh crusts have a glassy to silky sheen; dull, scuffed bubbles have been handled or packed badly.
- Coverage. Full blue coverage of one face beats scattered blue on brown matrix.
- Damage. Look for crushed or flattened bubbles on the high points, which do not repair.
- Weight and size. Price large plates per piece rather than per gram; a stated weight and dimensions let you compare listings.
From what we stock:
- Botryoidal Blue Hemimorphite 0.5 kg: about 7 x 3 x 2 inches and roughly 534 g of electric blue botryoidal crust, the high-end display form described above.
- Chrysocolla: palm stones and tumbles of the copper silicate most often confused with blue hemimorphite; side by side, chrysocolla is lighter and softer.
- Wulfenite Cluster on Matrix from Maoniuping Mine, Sichuan, China: 2.5 x 1.25 x 2 inches and 79 g; wulfenite is a lead mineral that grows alongside hemimorphite at classic localities such as Bleiberg, Austria.
- Azurite on Matrix: a copper oxidation zone mineral to compare with the zinc version of the same weathering story.
Digital Towns Market
Hemimorphite in stock
Frequently asked questions
Is blue hemimorphite natural?
Yes, natural electric blue botryoidal hemimorphite comes mainly from Yunnan Province, China. Color that runs evenly through the bubbles is a good sign; color pooled in crevices or sitting as a film suggests dye or paint, which is worth asking the seller about.
Is hemimorphite rare?
The mineral is common in weathered zinc deposits, but most of it is dull white, gray or brown. Bright blue botryoidal plates, large clean crystals and faceted stones are uncommon and priced accordingly.
What is the difference between hemimorphite and smithsonite?
Hemimorphite is a zinc silicate with SG 3.4 to 3.5 and one perfect cleavage. Smithsonite is a zinc carbonate, heavier at SG 4.3 to 4.5, fizzes in cold dilute hydrochloric acid and has rhombic cleavage. Both were once sold as calamine.
Can hemimorphite get wet?
Brief contact with water and mild soap is fine. Do not soak matrix pieces, because the host rock can hold water and stain, and avoid acids and ultrasonic cleaners. Dry botryoidal crusts thoroughly, since water lingers in the crevices.
Why is it called hemimorphite?
From the Greek for half and form. Its crystals end differently at each end of the main axis, a rare trait called hemimorphism, which also makes the crystals pyroelectric when warmed.
Sources
- Geology.com, Hemimorphite: https://geology.com/minerals/hemimorphite.shtml
- Minerals.net, Hemimorphite: https://www.minerals.net/mineral/hemimorphite.aspx
- International Gem Society, Hemimorphite Value, Price, and Jewelry Information: https://www.gemsociety.org/article/hemimorphite-jewelry-and-gemstone-information/
- webmineral, Hemimorphite Mineral Data: http://webmineral.com/data/Hemimorphite.shtml
- Geology.com, Smithsonite: https://geology.com/minerals/smithsonite.shtml
- International Gem Society, Smithsonite Value, Price, and Jewelry Information: https://www.gemsociety.org/article/smithsonite-jewelry-and-gemstone-information/