01 · Red
Erythrite Co₃(AsO₄)₂·8H₂O
crimson bloom on grey rock → pale crimson
#f1c4c2 · L* 83.0 · C* 17.0 · h 23.8°
Coldbank Rake · 2 November 2024
The register
Fifteen specimens off one upland district, each rubbed once across the same unglazed porcelain plate and listed in the order the powder puts them in.
£18 a specimen. A streak taken on the plate, the colour measured off the photograph, and the piece posted back with its entry in the register.
Send a specimen Or read the entries by date
Read within a fortnight of arriving · Haverskeld, in the north-west of the county · 0113 496 0271
02 · Red
Cinnabar HgS
vermilion, dull to bright → scarlet
#dd5551 · L* 54.5 · C* 61.3 · h 29.9°
Sarnwell Sough · 14 March 2025
03 · Red
Hematite Fe₂O₃
steel grey, metallic → red-brown
#8d4e41 · L* 40.4 · C* 32.0 · h 37.7°
Ladgill Level · 21 June 2024
04 · Yellow
Realgar AsS
orange-red, resinous → orange-yellow
#f2af51 · L* 76.1 · C* 58.6 · h 74.2°
Sarnwell Sough · 8 September 2025
05 · Yellow
Limonite FeO(OH)·nH₂O
dark brown, botryoidal → yellow-brown
#c19d67 · L* 66.8 · C* 33.8 · h 79.4°
Tarnbeck Hush · 30 August 2024
06 · Yellow
Sulfur S
lemon yellow, resinous → pale yellow
#f8f7dc · L* 96.7 · C* 13.5 · h 106.9°
Whinstone Spoil · 19 January 2026
07 · Green
Atacamite Cu₂Cl(OH)₃
dark emerald, glassy → apple green
#aed575 · L* 80.6 · C* 51.5 · h 123.2°
Ravenholme Vein · 30 May 2025
08 · Green
Malachite Cu₂CO₃(OH)₂
deep green, banded → pale green
#c7d5c2 · L* 83.8 · C* 11.2 · h 136.2°
Ravenholme Vein · 27 September 2024
09 · Green
Aurichalcite (Zn,Cu)₅(CO₃)₂(OH)₆
pale blue-green tufts → pale blue-green
#adcdc8 · L* 79.9 · C* 11.5 · h 187.2°
Ravenholme Vein · 16 November 2025
10 · Blue
Azurite Cu₃(CO₃)₂(OH)₂
deep blue, glassy → pale blue
#77a1dc · L* 65.5 · C* 34.0 · h 272.0°
Ravenholme Vein · 11 February 2025
The circle ends here. Below chroma 8 a hue angle is arithmetic on two numbers that are both nearly zero, so the next four have a lightness and nothing else, and they run from the palest down.
11 · No hue
Rhodochrosite MnCO₃
rose pink, banded → white
#c9c2b8 · L* 78.8 · C* 5.8 · no hue
Coldbank Rake · 8 February 2026
12 · No hue
Galena PbS
lead grey, metallic → lead grey
#898987 · L* 57.1 · C* 1.2 · no hue
Ladgill Level · 17 May 2024
13 · No hue
Pyrite FeS₂
brass yellow, metallic → greenish black
#3a413c · L* 26.7 · C* 4.8 · no hue
Dowlas Gill · 5 April 2024
14 · No hue
Magnetite Fe₃O₄
black, metallic → black
#3c3c3c · L* 25.5 · C* 0.0 · no hue
Tarnbeck Hush · 23 July 2025
And one that is on neither arm. Above Mohs 6.5 a mineral does not powder against porcelain — it cuts it. There is nothing to read, so there is nothing to sort.
15 · No streak
Quartz SiO₂
colourless to milky → none
no streak · Mohs 7 · harder than the plate
Whinstone Spoil · 2 March 2024
Why this order
A streak is the colour of a mineral's powder, and it is a property of the mineral rather than of the lump in front of you. It is also, often, nothing like the lump: pyrite is brass and streaks a greenish black, hematite is steel grey and streaks red. Sorting by it puts specimens together that do not look alike and separates ones that do, which is the whole of why the test is worth taking.
The gap
Laid out as angles, the fifteen leave one long stretch of the circle empty: 272° → 23.8°, 111.8° of it. Nothing in this district streaks magenta or violet, and as far as the plate is concerned nothing much anywhere does. The colour this page is printed on sits in the middle of that gap, at 328.1° — so no field on this site can be mistaken for a streak.
Send one in
Anything that will fit in a jiffy bag and does not need a licence. It is rubbed on the plate, photographed on the same sweep as the fifteen above, measured, and posted back to you with what it turned out to be.
£18 a specimen · Read within a fortnight of arriving