Is magnesite the same as howlite
No. Magnesite is a carbonate at density 3.00, howlite a borosilicate at 2.53 to 2.59. Both are dyed blue and sold as turquoise, and hardness cannot part them.
No. They are unrelated species that happen to do the same job in the trade. Magnesite is a magnesium carbonate at density 3.00 and hardness 3.5 to 4.5; howlite is a calcium borosilicate at density 2.53 to 2.59 and hardness 3.5. Both are porous white nodular material that takes dye, and both are sold dyed blue as imitation turquoise.
In short
- Hardness separates the imitations from turquoise and not from each other. Turquoise is hardness 5 to 6; magnesite starts at 3.5 and howlite is 3.5 flat. A steel point marks both fakes easily and struggles on turquoise, so one scratch answers the expensive question and none of them answers the other one.
- Density does separate them, by 15.8% to 18.6%. Magnesite is 3.00 and howlite 2.53 to 2.59. Worked through: an object that weighs 20.00 g as turquoise, 6.99 cubic centimetres, weighs 20.98 g as magnesite and about 17.90 g as howlite. A cheap scale and a glass of water resolve a 3 g difference on a 20 g bead comfortably.
- Acid is decisive and destructive. Magnesite is a carbonate and reacts with dilute acid; howlite is a borosilicate and does not. One drop on a hidden spot settles it permanently, and it also damages the specimen permanently, so it is a last resort rather than a first one.
- Magnesite fluoresces and howlite does not. The Handbook records magnesite as possibly showing pale green to pale blue fluorescence and phosphorescence under ultraviolet, and as triboluminescent. Howlite's sheet records no luminescence at all. A lamp is a non-destructive first try, and a negative proves nothing.
- Neither is a fake in itself. Undyed magnesite and howlite are legitimate collectable species, and howlite is a genuinely interesting borate. The deception is in the dye and the label, and a dealer who says dyed howlite is doing nothing wrong.
| Property | Turquoise | Magnesite | Howlite |
|---|---|---|---|
| Formula | CuAl6(PO4)4(OH)8·4H2O | MgCO3 | Ca2B5SiO9(OH)5 |
| Class | Phosphate | Carbonate | Borosilicate |
| Hardness | 5 to 6 | 3.5 to 4.5 | 3.5 |
| Density, measured | 2.86, less if massive | 3.00 | 2.53 to 2.59 |
| Weight of a 6.99 cm3 object | 20.00 g | 20.98 g | About 17.90 g |
| Reacts with dilute acid | No | Yes, it is a carbonate | No |
| Fluorescence on the sheet | None recorded | Pale green to pale blue under UV; also triboluminescent | None recorded |
| Usual form in the trade | Nodules and veins, natural blue | Dyed blue or blue-green; often with dark veining | Dyed blue; white with grey to black veining when undyed |
| Occurrence | Altered porphyry copper deposits and phosphate-rich sediments | Altered serpentine and peridotite; evaporites; veins | Borate deposits |
The two-step that actually works, in order
Step one: is it turquoise at all? Try a steel point on an inconspicuous spot. Turquoise is hardness 5 to 6 and resists it; magnesite at 3.5 to 4.5 and howlite at 3.5 both mark easily. This is the step that answers the question that has money attached to it, and it costs nothing.
Step two: which imitation is it? Hardness cannot do this. Magnesite and howlite both begin at 3.5 and the ranges touch. Density can, and the gap is not subtle: 3.00 against 2.53 to 2.59 is 15.8% to 18.6%.
Worked through on a real object, so the numbers can be substituted. Take a 20.00 g bead of genuine turquoise at density 2.86. Its volume is 20.00 ÷ 2.86 = 6.99 cm³. Now ask what a bead of that same size weighs in each material: magnesite at 3.00 gives 6.99 × 3.00 = 20.98 g; howlite at 2.56, the middle of its range, gives 6.99 × 2.56 = 17.90 g. Magnesite is about a gram heavier than turquoise and howlite is about two grams lighter, on a 20 g object, and the two imitations differ from each other by roughly 3 g.
That is well within the reach of a kitchen scale reading to 0.1 g and a water-displacement measurement. The method, and the traps in it — porous material absorbs water and reads light, and dye and stabilising resin both shift the answer — is on how to measure specific gravity at home. On a porous dyed nodule the measurement is genuinely less reliable than on a solid crystal, and that caveat matters more here than usual.
The tests that are decisive, and what they cost you
Acid: decisive, destructive. Magnesite is MgCO3 and reacts with dilute acid. Howlite is a calcium borosilicate and does not. A single drop of dilute hydrochloric acid on a hidden spot gives an unambiguous answer in seconds. It also etches a permanent pit. On a cheap tumbled stone that is a fair trade; on a finished piece of jewellery or a good specimen it is not, and no responsible dealer would do it to stock. Acid on carbonates generally is covered on how to remove calcite from a specimen.
Ultraviolet: non-destructive, suggestive. The Handbook of Mineralogy records magnesite as possibly exhibiting pale green to pale blue fluorescence and phosphorescence under ultraviolet, and as triboluminescent. Howlite's sheet records nothing of the kind. So a pale blue-green glow is a point towards magnesite; no glow proves nothing, because the Handbook's word is may. What that hedging means in practice is on whether fluorite is UV reactive, which is the same problem in a better-known species.
Appearance: free, weak, and worth doing first anyway. Undyed howlite is white with grey to black veining and is often nodular with a chalky to porcelaneous texture. Undyed magnesite is white to pale yellow or brown, commonly with a more even texture. Once both are dyed the veining is what people read, and dyed howlite's dark web is the classic imitation-turquoise look. Dye tests are on how to tell if a crystal is dyed and the turquoise-specific case on how to tell real turquoise from fake.
Who each of these is wrong for
Dyed material is wrong for a species collection, full stop. Not because it is fake — it is real magnesite or real howlite — but because the dye conceals the properties you would collect it for and cannot be reversed. A dyed nodule is an ornament.
Magnesite is wrong for anyone who will ever put it near acid. It is a carbonate, so an acid clean anywhere in the same bath destroys it, and even the acetic vapour from some cabinet materials will dull a polished surface over years.
Howlite is wrong for anyone who wants a crystal. The Handbook records crystals tabular on {100} only to 1 cm, and describes it as most commonly nodular. Crystallised howlite is a genuine rarity and almost nothing in circulation is it.
And turquoise itself is wrong for anyone buying on price. Stabilised, reconstituted and dyed turquoise are all widespread, disclosed treatment is normal in the trade, and GIA on gem treatments is the standard reference on what disclosure should look like. The reason this whole question exists is that natural untreated turquoise is scarce and the market for the colour is not.
The rest of this section is indexed at the collecting guides. We hold no catalogue and nothing on this site is offered for sale — the wanted list is the only commercial route, and undyed crystallised howlite and good magnesite are both things we look for, as is turquoise with locality data.