Is aragonite crushed coral?
No. Aragonite is a mineral species, Ca(CO3), hardness 3.5 to 4. Stony coral skeletons are made of it (USGS), but most aragonite specimens were never coral.
No, not as a rule: coral is one source of aragonite, not the other way round. Aragonite is the mineral Ca(CO3), hardness 3.5 to 4, density 2.95; the USGS says stony coral skeletons are made of it, so crushed stony coral is mostly aragonite. But the Handbook lists aragonite from caves, hot springs, evaporites and ore deposits, and calcite occurs in precious Corallium coral.
In short
- Coral is aragonite; aragonite is not coral. The USGS Fact Sheet 2010-3085, Corals as Climate Recorders says corals deposit a skeleton made up of the mineral aragonite, a form of calcium carbonate (CaCO3), and the USGS Coral Reef Facts page that reef corals secrete hard calcareous (aragonite) exoskeletons. The Handbook of Mineralogy aragonite sheet lists marine shells and skeletons among many settings: warm marine precipitate, evaporites, hot-spring sinter, cave dripstone, blueschist rocks, basalt amygdules.
- Is aragonite calcium carbonate? Yes. The September 2026 IMA-CNMNC Master List gives Ca(CO3), G, 1791, Spain. Worked on standard atomic weights: 40.04% calcium, CaO 56.03%, CO2 43.97%, the sheet’s ideal column to the second decimal. calcite and vaterite share the formula; why they are separate species is on is aragonite a polymorph of calcite.
- The three-question coral rule. Stony (scleractinian) or precious coral? Modern or fossil? Organism or mineral deposit? Modern stony coral is aragonite (USGS); the Yuyama and Higuchi (2019, PeerJ) paper states calcite occurs in precious corals (genus Corallium); Takada et al. (2017, Scientific Reports) describe calcite overgrowth on fossil coral skeletons after diagenesis; and a mine-run aragonite crystal was never coral.
- Documented failure: coralloidal is not coral. The aragonite sheet lists coralloidal among its habits, alongside globular, reniform, pisolitic and stalactitic. That is a shape, not an organism. This page found no source giving a hand test that separates coral-like mineral aragonite from coral rubble; DeCarlo (2018, Nature Communications) describes Raman spectroscopy as the tool that distinguishes calcite, aragonite and vaterite.
- What the balance can and cannot say. Solid aragonite reads 13.22 g in water for a 20.00 g piece at D 2.95, calcite 12.62 g at 2.7102, as on the live aragonite pages. Coral is porous, and no fetched source gives a bulk coral density, so this page gives none. No source we would cite defines “crushed coral” as a product, so this page describes material, not products.
| Material | Mineral | Source | Is it coral? | Can a collector tell by hand? |
|---|---|---|---|---|
| Modern stony (scleractinian) coral skeleton | Aragonite | USGS Fact Sheet 2010-3085; USGS Coral Reef Facts | Yes | Not the mineral: aragonite and calcite look alike as rubble |
| Deep-sea stony coral (Lophelia pertusa) | Aragonite | USGS WaterWords: Aragonite | Yes | No |
| Precious coral, genus Corallium | Calcite occurs | Yuyama and Higuchi 2019 | Yes, but not aragonite | No |
| Juvenile stony coral grown at low seawater Mg/Ca (laboratory) | >90% calcite, <10% aragonite | Yuyama and Higuchi 2019 | Yes, experimental | No |
| Fossil coral after diagenesis | Aragonite with secondary aragonite and calcite overgrowth possible | Takada et al. 2017; sheet: converts to calcite over geologic time | Was | No; screened by X-ray, thermoluminescence and other laboratory methods |
| Coralloidal, stalactitic or pisolitic aragonite (cave, mine) | Aragonite | Handbook aragonite sheet, Crystal Data | No: coral-shaped | Sometimes by setting, not by shape |
| Aragonite crystals from sheet localities (Molina, Agrigento, Tsumeb, Touissit…) | Aragonite | Handbook aragonite sheet, Distribution | No | Yes: crystals and twins |
| Solid aragonite, 20.00 g in water | 13.22 g (D 2.95) | Sheet D(meas.) | — | Confirms aragonite against calcite (12.62 g); not coral |
Is crushed coral aragonite? For stony coral, yes
The USGS statements. The USGS Fact Sheet 2010-3085, Corals as Climate Recorders reads: corals deposit a skeleton made up of the mineral aragonite, which is a form of calcium carbonate (CaCO3). Its seasonal light and dark bands, seen in X-radiographs, record one year of growth per couplet, and variations in the chemical and isotopic composition of the aragonite skeleton reflect seawater temperature, salinity and pH. The USGS Coral Reefs as Climate Archives page makes the same statement. The USGS Coral Reef Facts page says coral reefs are formed by huge colonies of corals that secrete hard calcareous (aragonite) exoskeletons, and the USGS WaterWords: Aragonite that both warm- and cold-water scleractinian corals, including the deep-sea Lophelia pertusa, produce their skeletons using aragonite.
So the narrow answer. Stony coral broken into pieces is aragonite, as far as these sources go. DeCarlo (2018) opens with the same point: it is well known that scleractinian coral skeletons are composed of the calcium carbonate mineral aragonite. None of the sources fetched describes any commercial crushed-coral product, and this page does not either. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.
Is aragonite crushed coral? Usually not
The mineral’s own record. The Handbook of Mineralogy aragonite sheet lists the settings in its Occurrence field: a primary precipitate in warm marine waters, as oolites and carbonate mud, a principal detrital sedimentary component as the hard parts of many marine micro-organisms, shells and skeletons; also from evaporite deposits; in sinter at hot springs and dripstone in caves; characteristic of high-pressure, low-temperature (blueschist facies) metamorphism; as amygdules in basalt and andesite; a secondary component in altered ultramafic rocks. Coral is one entry within one of those clauses.
The specimen record. Its Distribution field names mineral localities, not reefs: Molina, Guadalajara, Spain; Racalmuto, Cianciana and Agrigento, Sicily; Špania Dolina, Slovakia; the Erzberg and Leogang, Austria; Frizington and Cleator Moor, Cumbria; the Touissit mine and Tazouta, Morocco; Tsumeb, Namibia; caves at Bisbee, Arizona; Lake Arthur and Santa Rosa, New Mexico; the Passaic mine, Sterling Hill, New Jersey. The sheet records crystals to 30 cm and pseudohexagonal trillings; the trilling is explained on the aragonite page. Telling those crystals from calcite is on is aragonite the same as calcite.
Not all coral is aragonite: the exceptions
Precious coral. Yuyama and Higuchi (2019, PeerJ), a study of the stony coral Acropora tenuis, writes that aragonite is common in modern scleractinian corals, although calcite occurs in precious corals (genus Corallium) as well as foraminifera. The same paper reports that juvenile corals raised in low-magnesium seawater (Mg/Ca 0.5) built mixed skeletons of more than 90% calcite and less than 10% aragonite, against an aragonite-specific pattern at the natural ratio of 5.2. That is a laboratory result, cited here only to show that the mineral is not fixed by the word coral.
Fossil coral. Takada et al. (2017, Scientific Reports) write that diagenetic alteration of aragonite coral skeletons changes their chemical and isotopic compositions, and describe secondary aragonite precipitation and calcite overgrowth on primary aragonitic coral skeletons, which they screen for with thermoluminescence. The aragonite sheet’s own first sentence under Occurrence is that it converts to calcite over geologic time. An old coral, or a fossil one, may therefore be partly calcite.
Coralloidal aragonite and other look-alikes
The habit word. The sheet gives aragonite’s aggregate habits as columnar crystal aggregates and crusts, globular, reniform, pisolitic, coralloidal, stalactitic, internally fibrous or banded. Coralloidal means coral-shaped. A branching white aragonite from a cave or a mine is a mineral deposit, and the FMS database includes an entry titled Coral-Like Formation of Aragonite, from Mexico, among its aragonite records; by its title it is a coral-like mineral formation, not coral.
Documented failure: nothing in the hand settles it. Coral rubble, coralloidal aragonite and calcite can all be white and branching, and this page found no hand test that separates them; acid is left out because it attacks both polymorphs. DeCarlo (2018, Nature Communications) notes that Raman spectroscopy is particularly effective at distinguishing calcite, aragonite, vaterite and amorphous phases; that is a laboratory route. The name blue aragonite is discussed on is smithsonite the same as aragonite. For porous pieces the balance reads low; see how to measure specific gravity at home.
Is aragonite the same as coral calcium? Calcium carbonate, worked
The arithmetic. CaCO3 has a formula mass of 100.09; calcium is 40.04% of it, CaO 56.03% and CO2 43.97%. The sheet prints those oxides, 56.03 and 43.97, as its ideal column (2), and a Matsushiro, Japan analysis of 55.96 and 43.95 with 0.03 MgO. The cell, a 4.9611, b 7.9672, c 5.7407 Å with Z = 4, gives 2.930, the printed D(calc.); the measured value is 2.95. These are mineral numbers, not a statement about any supplement, and this page gives no health or dietary advice.
Hazard questions, in one line. Anything about toxicity is routed to toxic minerals in a collection; that is not advice. Whether coral-derived or mineral aragonite glows under a lamp is a separate question, on is aragonite fluorescent. More identification guides are in the collecting guides.