HY (Հայերեն)
Mineral family
The metallic ores
Three stones that do something you can see. Hematite streaks blood red however black it looks. Pyrite strikes sparks and grows in perfect cubes. Lodestone picks up iron. In a world without chemistry, these behaviours demanded explanation, and the explanations are still with us.
At a glance
Hematite, pyrite and lodestone. Heavy, metallic, magnetic or shining, and the group whose observable oddities generated the most folklore per stone.
- Keynote
- The metals that behave strangely
- Chemistry
- oxides & sulfides
- Crystal systems
- Trigonal & cubic
- Mohs range
- 5.5 to 6
- Stones here
- 3 in the catalogue
- Care rule
- Keep dry. Pyrite in particular will damage neighbouring specimens as it decays.
- Watch for
- Magnetic hematite, which is a manufactured ceramic; pyrite decay in humid storage.
Themes
weight
direction
attraction
the red streak
fire from stone
what behaves visibly
What holds the family together
Hematite is iron oxide, Fe2O3, and its name comes from the Greek for blood, because whatever colour the specimen appears, its streak, the powder it leaves when dragged across unglazed porcelain, is deep red. Polished hematite looks like dark metal; the same material finely divided is red ochre, the oldest pigment in human use.
Pyrite is iron sulfide, FeS2, cubic, and it grows in cubes and pyritohedra so regular that people encountering them for the first time assume they were cut. Its name comes from the Greek for fire, because it strikes sparks against steel, a use going back to the Neolithic. Its brassy lustre is why it is called fool's gold, and the distinction from gold is easy: gold is soft, heavy and malleable, pyrite is brittle and will shatter.
Lodestone is magnetite, Fe3O4, that has been naturally magnetised, probably by lightning strikes. It is the material of the first compasses, described in Han dynasty China and later in Europe, and every folk belief about attraction and drawing things towards you traces back to something that visibly does that.
How it forms
Hematite forms in sedimentary banded iron formations, which are among the oldest large-scale rock units on earth and record the oxygenation of the oceans over two billion years ago. It also forms in hydrothermal veins, where it produces the specular and kidney-ore varieties.
Pyrite forms in a huge range of settings: hydrothermal veins, sedimentary rocks including coal, and as replacement fossils, which is why some ammonites come out of the ground gold.
Magnetite forms in igneous and metamorphic rocks and is common as a black sand in stream beds. Only a small fraction becomes naturally magnetised into lodestone, and the leading explanation is lightning striking exposed magnetite at the surface.
Historically these ores mattered economically before they mattered decoratively. Elba's hematite supplied Etruscan and Roman iron; pyrite was mined for sulfuric acid production into the twentieth century.
The stones of this family
- Hematite (Fe₂O₃, Mohs 5.5). Iron oxide that streaks blood red however black it looks, which is where its name and its whole reputation come from. Ochre from it is the oldest pigment we have.
- Pyrite (FeS₂, Mohs 6). Fool's gold, in natural cubes so perfect they look cut. Struck for fire since the Neolithic, and unstable in humid air, where it can crumble and give off acid.
- Lodestone (Fe₃O₄, magnetised, Mohs 6). Naturally magnetised magnetite, the material of the first compasses in Han China and the root of every folk practice about attraction.
Trade names and lookalikes
The single most common mislabelling in this family is magnetic hematite, sold as tumbled stones, bracelets and beads that stick to each other. Natural hematite is not magnetic in any noticeable way. The magnetic material is a manufactured barium or strontium ferrite ceramic, sometimes called hematine, and it is not a mineral at all. It is a perfectly reasonable product; it is simply not hematite.
Pyrite is rarely faked, since it is cheap. Its problem is decay: in humid conditions it oxidises to iron sulfates, expanding and cracking the specimen and producing sulfuric acid that damages labels, boxes and neighbouring minerals. A pyrite specimen that develops white powder or a sulfurous smell should be isolated.
Marcasite in jewellery is almost always pyrite, since true marcasite is too unstable to set. Lodestone sold with iron filings clinging to it is genuine; a magnet with a stone glued on is not.
Care that follows from the structure
Keep the whole family dry. Pyrite decay is the most serious storage problem in mineral collecting, and low humidity is the only reliable prevention. Store pyrite separately from paper, cardboard and other specimens.
Hematite is stable and hard at 5.5 to 6.5 and takes daily wear well, but the polish can be dulled by abrasives and the stone can rust at the surface if kept wet.
Lodestone loses magnetism if heated strongly or struck hard.
None of these should be used for direct-contact gem waters. Pyrite in water produces acid; hematite will discolour it; and the general principle for sulfide minerals is that they belong nowhere near anything you intend to drink.
Հարցեր մտորումների համար
- What am I attracted to, and is the pull mine or the object's?
- Where do I mistake the appearance of value for the thing itself?
- What in my life is quietly corroding because I have stored it badly?
Stones in this family
Frequently asked questions
Վերջին գրառումներ
Բացահայտեք Տարոտ քարտերի հին իմաստությունը և բացեք ձեր հոգևոր ճանապարհորդության գաղտնիքները: Մեր բլոգը ձեր դարպասն է Տարոտ ընթերցման հարուստ խորհրդանիշների, իմաստների և գործնական կիրառությունների հասկացման համար։
