Species
Mineral species notes for collectors: formula, hardness, habit, and the localities that produce the best specimens, with the tests that separate look-alikes.
These notes cover the species a British collection is built on: fluorite at hardness 4 with perfect octahedral cleavage, pyromorphite at 3.5-4 in hoppered green prisms, cassiterite at 6-7 and a density near 7, and scorodite, a hydrated arsenate common as a crust and rare as a gemmy crystal.
Fluorite
The most collected British mineral, and the one where locality does most of the work in setting a price. CaF2, hardness …
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Pyromorphite
A lead phosphate that produces some of Britain's most distinctive specimens, including the barrel-shaped campylite …
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Cassiterite
The mineral that funded Cornwall. Tin dioxide at hardness 6 to 7 and a density near 7, and at its best forming the elbow…
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Scorodite
Common as a dull crust, rare as a transparent blue crystal. The 2006 Hemerdon dig produced the latter, and it is what pu…
Read →Azurite
The deepest blue in mineralogy, and the species Tsumeb defined. It is also the one most likely to be quietly altering to…
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Smithsonite
A zinc carbonate that comes in almost every colour, usually as botryoidal crusts with a silky lustre unlike anything els…
Read →Vanadinite
The apatite-supergroup vanadate that turns up red-orange on Moroccan barite. Heavy at a density near 7, soft at hardness…
Read →Erythrite
Cobalt bloom: crimson blades at hardness 1.5 to 2.5, which is the single fact that governs how you buy one, how you clea…
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Wulfenite
PbMoO4, thin orange tablets out of the oxidised zone of lead mines, and the two Arizona localities that the whole of the…
Read →Adamite
The yellow-green arsenate that made Mapimí famous. Bright under shortwave ultraviolet, soft at hardness 3.5, and easy to…
Read →Dioptase
The green that persuaded eighteenth-century Moscow it had found emerald. Hardness 5, perfect rhombohedral cleavage, and …
Read →Mimetite
Mimetite is lead arsenate, hardness 3.5 to 4, named for imitating pyromorphite. Campylite from Dry Gill is the British f…
Read →Olivenite
Olivenite is a copper arsenate, hardness 3, from the oxidised copper zones of Cornwall. Habit, the series with adamite, …
Read →Pyrrhotite
Pyrrhotite is a non-stoichiometric iron sulphide, hardness 3.5 to 4.5, magnetic and unstable. Crystals to 40 cm, Dalnego…
Read →Vivianite
Vivianite is a hydrated iron phosphate, hardness 1.5 to 2, colourless when fresh and darkening to indigo and black. Corn…
Read →Atacamite
Atacamite is a copper chloride hydroxide, hardness 3 to 3.5, named for the Atacama Desert. Its polymorphs, the Cornish c…
Read →Pseudomalachite
Pseudomalachite is a copper phosphate, hardness 4.5 to 5, named from the Greek for false because it resembles malachite.…
Read →Hemimorphite
Hemimorphite is a zinc silicate, hardness 4.5 to 5, whose crystals are terminated differently at each end. Habit, the ca…
Read →Copper
Native copper is the metal itself, hardness 2.5 to 3 and a density of 8.95. Crystals reach 15 cm and masses of hundreds …
Read →Cuprite
Cuprite is copper oxide, hardness 3.5 to 4, density 6.14, with a refractive index of 2.849, higher than diamond. Crystal…
Read →Chalcocite
Chalcocite is Cu2S, hardness 2.5 to 3, density 5.5 to 5.8, crystals to 25 cm. Much material labelled chalcocite is reall…
Read →Rhodochrosite
Rhodochrosite is manganese carbonate, hardness 3.5 to 4, density 3.70, with perfect rhombohedral cleavage and crystals t…
Read →Cyanotrichite
Cyanotrichite is a blue copper aluminium sulphate in acicular tufts to 3 cm. Its hardness has never been determined. Den…
Read →Chalcosiderite
Chalcosiderite is the iron end of the turquoise series, hardness 4.5, density 3.22, crystals only 3 mm long. Cornwall is…
Read →Heulandite
Heulandite is a zeolite series, hardness 3.5 to 4, density 2.10 to 2.20, coffin-shaped crystals to 12 cm. Most labels om…
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