Anglesite or Galena?
Galena is metallic PbS with a lead-gray streak; anglesite is adamantine PbSO4 with a white streak and can coat galena. What a mixed piece weighs in water.
Galena if the piece is metallic and opaque with a lead-gray streak; anglesite if it is adamantine with a white streak. Galena is PbS, cubic, density 7.58; anglesite is PbSO4, orthorhombic, density 6.38, and its sheet records it banded around galena cores. A 20.00 g piece reads 17.36 g in water as galena and 16.87 g as anglesite.
In short
- Criteria first. On the two Handbook of Mineralogy sheets, four properties separate them: streak (lead-gray against white), lustre (metallic against adamantine, resinous to vitreous), transparency (opaque against transparent to opaque) and crystal system with cleavage (cubic, perfect {001}, against orthorhombic, {001} good). Two do not: hardness overlaps, and anglesite is commonly tinted gray.
- The core-fraction ladder. The anglesite sheet records it banded around a core of galena. Worked as 1/D = f/7.58 + (1 − f)/6.38, with f the galena share by mass, a 20.00 g piece reads 16.87 g as pure anglesite, 16.99 g at 25% galena, 17.11 g at 50%, 17.24 g at 75% and 17.36 g as pure galena: about 0.05 g per 10%.
- Documented failure: the cerussite collision. cerussite, PbCO3, density 6.55, reads 16.95 g, which is what anglesite with 16.4% galena by mass reads. The cerussite sheet also prints a white streak and adamantine lustre. The balance cannot tell a cored anglesite from cerussite; cerussite sets out what can.
- Who each label is wrong for. Galena is the wrong label for any part that streaks white, however galena-shaped the piece. Anglesite is wrong for a metallic part with a lead-gray streak. A banded piece needs both names, and the ladder gives its proportions only roughly.
- Not repeated here. The streak test and the rind volume arithmetic are on anglesite; lead content and its hazard on is galena toxic, which is not advice.
| Composition | Galena by mass | Galena by volume | Bulk density | 20.00 g in water | Above pure anglesite | Streak and lustre (sheet) |
|---|---|---|---|---|---|---|
| Anglesite, PbSO4 | 0% | 0% | 6.38 | 16.87 g | 0 | White; adamantine, resinous to vitreous |
| Anglesite with a galena core | 10% | 8.6% | 6.483 | 16.91 g | 0.04 g | Both, by zone |
| Cerussite, PbCO3 (for comparison) | — | — | 6.55 | 16.95 g | 0.08 g | White; adamantine, tending toward vitreous, resinous |
| Anglesite with a galena core | 16.4% | — | 6.55 | 16.95 g | 0.08 g | Both, by zone |
| Anglesite with a galena core | 25% | 21.9% | 6.643 | 16.99 g | 0.12 g | Both, by zone |
| Anglesite with a galena core | 50% | 45.7% | 6.928 | 17.11 g | 0.24 g | Both, by zone |
| Galena with an anglesite rind | 75% | 71.6% | 7.240 | 17.24 g | 0.37 g | Both, by zone |
| Galena with an anglesite rind | 90% | 88.3% | 7.440 | 17.31 g | 0.44 g | Both, by zone |
| Galena, PbS | 100% | 100% | 7.58 | 17.36 g | 0.50 g | Lead-gray; metallic |
Anglesite or galena? The four tests that decide
Streak, lustre, transparency and crystal system separate anglesite from galena on their Handbook sheets; hardness and a gray colour do not. The galena sheet gives PbS, cubic, lead-gray, metallic and opaque, with a lead-gray streak and perfect cleavage on {001}. The anglesite sheet gives PbSO4, orthorhombic, colorless to white and commonly tinted gray, or orange, yellow, green or blue, rarely violet; adamantine, resinous to vitreous; transparent to opaque; streak white; cleavage {001} good, {210} distinct. Method: how to use a streak plate.
What does not decide. Hardness is 2.5 to 2.75 for galena and 2.5 to 3 for anglesite, so a scratch test overlaps. Colour fails for gray anglesite. Fluorescence leans one way only: the anglesite sheet says it may fluoresce yellow under UV and the galena sheet prints nothing, but a may is not a test.
What the names mean. The IMA list gives galena PbS, status G, with the year printed as a question mark and the country unknown, and anglesite Pb(SO4), G, 1832, United Kingdom. The anglesite sheet names it for the island of Anglesey, Wales, and lists Parys Mountain among its localities; the galena sheet gives a Latin word for lead ore or the dross from melted lead. One is a sulfide, the other a sulfate of the barite group.
How are anglesite and galena found together?
The anglesite sheet records the mineral as banded around a core of galena and lists galena among its associates; it does not print a reaction or a mechanism. Its Occurrence field reads: common in the oxidized zone of lead deposits. Its habit list ends nodular, stalactitic, granular, massive, banded around a core of galena. Its associates include cerussite, leadhillite, lanarkite, caledonite, linarite and pyromorphite, all of them lead-bearing, and galena.
Galena’s side. The galena sheet places galena in many different types of environments, in hydrothermal veins formed under a wide range of temperatures, and names no anglesite among its associates. Neither sheet says how much galena becomes anglesite or how fast, and this page does not either. The mass and volume balance for a rind is worked on anglesite and is not repeated here.
Where both are named. Both sheets name Wanlockhead; the anglesite sheet adds Leadhills and Caldbeck Fells, and the galena sheet Alston Moor. See Leadhills-Wanlockhead, Caldbeck Fells and Alston Moor. The lead secondaries that grow with anglesite there include lanarkite, leadhillite, linarite and pyromorphite.
What does a banded piece weigh in water? The core-fraction ladder
The core-fraction ladder: each 10% of galena by mass inside anglesite raises the in-water reading of a 20.00 g piece by about 0.05 g. Method: for two phases with no pores, the bulk density is 1 divided by (f/7.58 + (1 − f)/6.38), where f is the galena share by mass and the densities are those measured on the sheets; the in-water reading is 20 − 20/D. Pure anglesite reads 16.87 g, 25% galena 16.99 g, 50% 17.11 g, 75% 17.24 g, pure galena 17.36 g. Run backwards, a reading of 17.11 g on a clean two-phase piece points to about half galena by mass. Method: how to measure specific gravity at home.
Documented failure: the cerussite collision. cerussite, at 6.55, reads 16.95 g, the same as anglesite with 16.4% galena by mass. Both of those print a white streak and an adamantine lustre on their sheets. So a white-streaking, adamantine piece that reads 16.95 g is either cerussite or galena-cored anglesite, and weight cannot say which; the cerussite page covers the separation.
What the ladder assumes. Two minerals only, no cavities and no rock. Real pieces carry matrix; the galena sheet lists calcite, barite and quartz among its associates, all lighter than either lead mineral, and any of them drags the reading down and makes a galena share look smaller than it is. At 0.05 g per 10%, a home balance reading to 0.01 g sees the change, but the ladder is a rough proportion, not an assay.
Who each label is wrong for
“Galena” is the wrong label for anything that streaks white; “anglesite” is the wrong label for anything metallic with a lead-gray streak. On a banded piece the honest label names both and says which is which, for example anglesite on galena. Where the outer layer is white-streaking and adamantine, the streak alone does not exclude cerussite, which is why the collision above matters. Labelling practice is on how to label and catalogue a mineral collection.
Lead content and other questions. Worked from the formulas, galena is 86.60% lead and anglesite 68.33%, the figures used on is galena toxic and anglesite. The magnetism question is on is galena magnetic. Lead hazard is on those pages and toxic minerals in a collection; nothing here is health advice. More identification guides are at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.