Hematite.

Hematite has a long history, stretching back to classic times, of being carved as seals: these are frequently set in signet rings. Tradition maintains that this stone bleeds when cut: apologists point out that the water used as a lubricate in the cutting process turns red with the fine powder.
       Hematite's associations with blood and iron made it a natural dedication to the Roman God of War - Mars, and it was very popular with soldiers, who smeared themselves with it to create a magical invulnerability.Recorded more than 2,050 years ago, in Babylon, is the tradition that Hematite, carried as a talisman, ensured that petitions would be successful, as would lawsuits and other issues necessitating legal judgements.
       Large specimens have been used as magical mirrors and employed for scrying. Smaller ones are often used to deflect negative influences, rather like a shield deflecting a sword. The crystal itself has a metallic sheen, and tumbled Specular Hematite is extraordinarily smooth and frictionless to handle, sometimes evoking the image of not only deflecting negativity but also being able to slip free of its clutches without effort.
       Iron Pyrites was made into jewellery by the classical Greeks, as it was by the Inca peoples. It can, like Specular Hematite, be ground and polished to make a highly reflective surface, a technique used in ancient Mexico, where natives used their expertise in stonecraft to create mirrors with one side completely flat, and the other strongly convex; this side was often also decorated with symbols to assist divination.
       American Indian Medicine Men frequently included Pyrites among their portfolio of treasures, and they were in regular currency as amulets. The ancient Chinese held them to have protective properties and even used them to ward off crocodiles. It is likely that their traditional earth symbol, a golden cube, was inspired by Pyrite. Even today the cube is deemed to represent the element of Earth, and employed as a means of "grounding" or "centring" magical or spiritual energy - in the form of an altar, for exmple.
       Pyrites have been used as a source of sparks, hence fire, since prehistoric times: the name itself is derived from the Greek word for fire. They were even employed instead of flint in early firearms.
       Pyrite nodules, when broken, reveal a solid sunburst of needle-like crystals radiating from the centre. Their shape and colour make them strongly symbolic of the Sun, and they can be employed as decorations to bring a sunlike warmth and brightness into the home.

Whilst it is harder than a knife blade, Quartz will scratch this mineral. Hematite (a.k.a. Iron Oxide) occurs in several different forms, but is always opaque. The form most frequently offered for sale is Specular Hematite (a.k.a. Looking Glass Ore). This is the crystal form of the mineral, and is silver-black and shiny. The epithet Specular is derived from the Latin meaning mirror; Hematite comes from the Greek meaning blood - referring to the colour of its other forms, notably Red Ochre which was used as paint by the famous Paleolithic cave artists. Red Ochre was also prominent in ancient burial customs. For example, around 15,000 years ago, during the latest full Ice Age, a young man was buried in Paviland Cave, West Glamorgan, covered in a sprinkling of this blood red mineral.
       Another form of Hematite is Kidney Ore which, as its name suggests, is rounded and knobbly; broken specimens exhibit their radiating fibrous crystals which can vary from dark grey to brick red. It is the main ore of Iron.
       Iron Pyrites (a.k.a. Iron Sulphide) are pale brass or bright golden coloured, and have frequently been mistaken for gold by over-optimistic prospectors (hence the colloquial name: Fool's Gold, which is a legacy of the heady Gold Rush days). To add to the confusion the two minerals often occur side by side!
       The incorruptible quality which gold is so famous for is not shared by Pyrites, which can corrode easily - even just in the presence of air. Fragile specimens such as some pyritized fossils, created where pyrites replace the shells of marine organisms for example, can decompose in the space of mere months.
       Its naturally occurring crystal shape is cubic, although it often forms striated, intersecting cubes. Pyrites are always opaque, and are found throughout Britain, for example in the Slates of North Wales and, as nodules, in the Clay of South East England. It is widespread throughout the world, in igneous, sedimentary, and metamorphic rocks.
       Specular Hematite, the gem quality variety, is found in England, notably in Cumbria; the Isle of Elba is also renowned for producing excellent specimens. The other varieties are far more common and are found all over the world.