Chlorargyrite
Chlorargyrite, AgCl: cubic silver chloride, hardness 2.5, density 5.556, sectile and very plastic, turning violet-brown to purple in light. It is 75.26% silver.
Chlorargyrite is silver chloride, AgCl, an IMA species (A, 1962 s.p., Germany): cubic, hardness 2.5, density 5.556, sectile and very plastic, colourless to pale yellow or gray, turning violet-brown to purple on exposure to light. It is 75.26% silver. Bromargyrite, AgBr, is 0.51 g heavier in water per 20 g; iodargyrite, AgI, has a yellow streak.
In short
- The silver-halide ledger. Three independent scans of the September 2026 IMA-CNMNC Master List find 4 rows written in silver and a halogen alone: chlorargyrite (AgCl), bromargyrite (AgBr), iodargyrite (AgI) and miersite (AgI). Worked on standard atomic weights, silver by mass is 75.26%, 57.45%, 45.95% and 45.95%. The Handbook of Mineralogy prints miersite as (Ag,Cu)I.
- The two-split rule. Worked as 20 − 20/D, a 20.00 g piece reads 16.40 g in water as chlorargyrite and 16.91 g as bromargyrite, 0.51 g apart: weigh it to split chloride from bromide. Iodargyrite reads 16.49 g and miersite 16.45 g, less than 0.1 g from chlorargyrite, so weight fails there; their sheets give a yellow and a canary-yellow streak against chlorargyrite’s white, and a perfect cleavage where chlorargyrite has none printed.
- Light, as printed. The chlorargyrite sheet: colourless, pale yellow, gray; turns violet-brown to purple on exposure to light. The iodargyrite sheet: colourless, becoming yellow on exposure to light. The bromargyrite and miersite sheets print no response to light. This page adds no mechanism and no storage advice; see which minerals fade in light.
- Plastic, not brittle. The sheet calls chlorargyrite sectile and ductile, very plastic, with hardness 2.5, and its lustre resinous to adamantine, waxy. Cerussite, an associate on the same sheet with a white streak too, is very brittle at 3 to 3.5 and reads 16.95 g in water.
- Where. The Distribution field names exceptional masses at Broken Hill, New South Wales, extraordinary masses in the Lake Valley district, New Mexico, and Chañarcillo, Chile, with Saxony, Joachimsthal, Cornwall and Mexico. The occurrence line: may be a rich ore in the oxidized zone above silver deposits, commonly preserved in arid climates.
| Name | Formula (IMA) | IMA status | Silver by mass | System | Hardness | Density | 20.00 g piece in water | Streak | Cleavage | Light (sheet) |
|---|---|---|---|---|---|---|---|---|---|---|
| Chlorargyrite | AgCl | A, 1962 s.p., Germany | 75.26% | Cubic | 2.5 | 5.556 | 16.40 g | White | None printed | Turns violet-brown to purple |
| Bromargyrite | AgBr | A, 1962 s.p., Mexico | 57.45% | Cubic | 2.5 | 6.474 | 16.91 g | White to yellowish white | None printed | None printed |
| Iodargyrite | AgI | A, 1962 s.p., Mexico | 45.95% | Hexagonal | 1.5 | 5.69 | 16.49 g | Yellow, shining | {0001}, perfect | Colourless, becoming yellow |
| Miersite | AgI; Handbook (Ag,Cu)I | G, 1898, Australia | 45.95% | Cubic | 2.5 | 5.64 | 16.45 g | Canary-yellow | {011}, perfect | None printed |
| Cerussite (associate, not a halide) | Pb(CO3) | G, 1845 | 0% | Orthorhombic | 3 to 3.5 | 6.55 | 16.95 g | White | Two good, two poor | None printed |
What is chlorargyrite? Silver chloride, AgCl
Chlorargyrite is silver chloride, one silver to one chlorine, AgCl. The Handbook of Mineralogy chlorargyrite sheet gives it cubic, point group 4/m 3 2/m, space group Fm3m, with crystals cubic, modified by {111} and {011}, to 1 cm, in parallel or subparallel groups; rarely as stalactites or columnar to coralloidal aggregates; fibrous; and commonly massive, forming crusts and films. The fracture is uneven to subconchoidal, it is sectile and ductile, very plastic, with hardness 2.5 and measured density 5.556.
What the IMA list records. The September 2026 list gives chlorargyrite, AgCl, status A, 1962 s.p. (in the list’s key, s.p. marks a special-procedure action in that year), with Germany as the country of first description and a second reference in Physical Review B 59 (1999), 750. The sheet names it for CHLORine and the Greek for silver, argyros. Its reference (1), Dana’s System of Mineralogy, 7th edition (1951), v. II, 11–15, carries the bracketed name [cerargyrite]; a case-insensitive scan of the IMA list finds 0 lines containing cerargyrite.
Its chemistry, worked. On standard atomic weights AgCl is 75.26% silver and 24.74% chlorine; the sheet’s Chañarcillo, Chile analysis is Ag 75.27, Cl 24.73. Its Broken Hill, Australia analysis carries bromine and iodine as well, Ag 67.28, Cl 14.36, Br 15.85, I 2.35. Which name such a mixed halide takes is the halogen check on is silver a mineral, not repeated here.
Chlorargyrite, bromargyrite and iodargyrite: the silver-halide ledger
Four IMA minerals are silver and a halogen alone, and chlorargyrite is the chloride. Method: the September 2026 list was converted with pdftotext -layout; a row parser, an independent field scan and a token scan over every line each kept formulas whose element symbols are silver plus one or more of F, Cl, Br and I. The parser and field scan found the same 4 rows, chlorargyrite, bromargyrite, iodargyrite and miersite, and the token scan found the same three formulas, AgCl, AgBr and AgI. Tocornalite, (Ag,Hg)I (?), is listed with status Q, questionable, and holds mercury, so it is outside the count.
What the sheets give each. Bromargyrite, AgBr, is cubic, hardness 2.5, density 6.474, sectile, ductile, very plastic, pale yellow, greenish brown or bright green, with a white to yellowish white streak; its sheet adds that it may give off a strong “medicinal” odor when exposed to air, and names Bisbee among its localities. Iodargyrite, AgI, is hexagonal, hardness 1.5, density 5.69, sectile and flexible, with a perfect {0001} cleavage and a yellow, shining streak. Miersite, AgI on the IMA list and (Ag,Cu)I on its sheet, is cubic, hardness 2.5, density 5.64, somewhat brittle, canary-yellow, with a perfect {011} cleavage.
Silver falls as the halogen gets heavier. Worked from the formulas: 75.26% in the chloride, 57.45% in the bromide, 45.95% in the iodides. Density does not follow the same order: the chloride is 5.556, the bromide 6.474, and the two iodides 5.69 and 5.64.
How do you tell chlorargyrite from bromargyrite and iodargyrite? The two-split rule
Weigh it to split chloride from bromide; streak it to split chloride from iodide. Worked as 20 − 20/D, a 20.00 g piece reads 16.40 g in water as chlorargyrite and 16.91 g as bromargyrite, 0.51 g apart, enough for a balance reading to 0.01 g. The method is on how to measure specific gravity at home.
Documented failure: the iodides. Iodargyrite reads 16.49 g and miersite 16.45 g, less than 0.1 g from chlorargyrite’s 16.40 g: a balance will not split them. The sheets do: chlorargyrite’s streak is white, iodargyrite’s yellow and shining, miersite’s canary-yellow; iodargyrite has a perfect {0001} cleavage and miersite a perfect {011}, while the chlorargyrite sheet prints no cleavage. Streak technique is on how to use a streak plate; reading a broken surface on cleavage or fracture.
Where the rule stops. Both sheets give chlorargyrite and bromargyrite as cubic, space group Fm3m, and the chlorargyrite sheet’s Broken Hill analysis holds both halogens. Neither sheet gives a density for such a mixture, so a reading between 16.40 and 16.91 g names neither end. A white crust that is very brittle and harder, at 3 to 3.5, is more likely cerussite, which reads 16.95 g. The hardness technique is on how to test mineral hardness properly.
Does chlorargyrite change colour in light?
Yes, as the sheet prints it: colourless, pale yellow, gray; turns violet-brown to purple on exposure to light. The sheet adds colorless to yellow or green in transmitted light. Of the four silver-halide sheets, two print a response to light: chlorargyrite’s, and iodargyrite’s colourless, becoming yellow on exposure to light. The bromargyrite and miersite sheets print none.
What this page does not add. The sheets give no mechanism, no rate and no threshold, and this page offers none, nor any storage recipe. The general question of light-sensitive species is on which minerals fade in light. The same Handbook series records acanthite, the silver sulphide, as photosensitive, and proustite and pyrargyrite as darkening with exposure to light.
Handling. Any question about handling silver minerals belongs on toxic minerals in a collection; nothing on this page is health or safety advice.
Where chlorargyrite is found: Broken Hill, Lake Valley and Chañarcillo
The Distribution field says only a few localities are given for fine crystals or exceptionally large or pure masses, and names Marienberg, Freiberg, Johanngeorgenstadt and Schneeberg, Saxony, and St. Andreasberg, Harz, Germany; Joachimsthal, Czech Republic; the Calstock, Cambourne (as the sheet spells it) and St. Just districts and elsewhere in Cornwall; Schlangenberg, Altai, Russia; the Poorman mine, Idaho; extraordinary masses in the Lake Valley district, Sierra Co., New Mexico; Tombstone and Richmond Basin, Arizona; Bullfrog and Rochester, Nevada; Santa Eulalia, Chihuahua, and Catorce, San Luis Potosí, Mexico; Chañarcillo, Caracoles and Huantajaya, Chile; and Broken Hill, New South Wales, in exceptional masses. The sheet’s X-ray powder pattern is from Cornwall material.
How and with what. The occurrence field reads may be a rich ore in the oxidized zone above silver deposits; commonly preserved in arid climates. The association line is silver, cerussite, iodargyrite, atacamite, malachite, jarosite and Fe–Mn oxides. Native silver is on native silver and the silver sulphide of the primary veins below on acanthite.
Weighing it. A 20.00 g piece of chlorargyrite reads 16.40 g in water. The rest of the reference section is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.