Arsenite? of Iron

The kindness of the Row W. Gregor was the pleasant cause of my becoming acquainted with this new mineral; he sent me a specimen in Sept, 1808, telling me that he had ascertained it to consist of Oxyde of Iron and Oxyde of Arsenic, but that he had not entered into an examination of it with a view to ascertain the relative quantities: it appears that nothing more has been done since that time, and it is with some hesitation that I publish it as an Arsenite, as it may hereafter possibly be proved to be an earthy Arseniate of Iron: it was found in a mass of rock which appears on a down in the parish of Ferrari Arwothel, Cornwall. Although it is not very interesting at first sight, yet its variety of colour is sufficiently striking to produce a desire for information, and it will be pleasant to recognise it in some other place.

The substance is in some parts compact, with a dull wax-like lustre, and of a bluish olive green; in other parts it is of an earthy texture and greenish white zoned with the olive green: rounded grains of Quartz are imbedded in it, which prevent the specific gravity from being taken, but it is not very heavy: it is stained here and there with Iron Ochre. The compact parts are harder than Iron, but readily scraped and splintered with a knife; the whiter parts yield to the finger nail: when heated it at first reddens, then melts with ebullition, giving out a slight scent of garlic, and it is at last rendered attractible by the magnet; the facility of its fusion seems to imply that it is not merely a mixture of its component parts, but a combination: its colour probably depends upon its containing water.