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  2. Hematite - Wikipedia

    en.wikipedia.org/wiki/Hematite

    Hematite (/ ˈ h iː m ə ˌ t aɪ t, ˈ h ɛ m ə-/), also spelled as haematite, is a common iron oxide compound with the formula, Fe 2 O 3 and is widely found in rocks and soils. [6] Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe 2 O 3. It has the same crystal structure as corundum ...

  3. Mohs scale - Wikipedia

    en.wikipedia.org/wiki/Mohs_scale

    Hardness may be difficult to determine, or may be misleading or meaningless, if a material is a mixture of two or more substances; for example, some sources have assigned a Mohs hardness of 6 or 7 to granite but it is a rock made of several minerals, each with its own Mohs hardness (e.g. topaz-rich granite contains: topaz — Mohs 8, quartz ...

  4. Superhard material - Wikipedia

    en.wikipedia.org/wiki/Superhard_material

    Most metal borides are hard; [41] however, a few stand out among them for their particularly high hardnesses (for example, WB 4, [42] [43] RuB 2, OsB 2 and ReB 2). These metal borides are still metals and not semiconductors or insulators (as indicated by their high electronic density of states at the Fermi Level ); however, the additional ...

  5. Bog iron - Wikipedia

    en.wikipedia.org/wiki/Bog_iron

    Even after improved smelting technology made mined ores viable during the Middle Ages, bog ore remained important into modern times, particularly in peasant iron production. [10] In Russia, bog ore was the principal source of iron until the 16th century, when the superior ores of the Ural Mountains became available. [citation needed]

  6. Limonite - Wikipedia

    en.wikipedia.org/wiki/Limonite

    Limonite (/ ˈ l aɪ m ə ˌ n aɪ t /) is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·nH 2 O, although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely.

  7. EDITORIAL: Hard time for hard wood - AOL

    www.aol.com/editorial-hard-time-hard-wood...

    The wood is desirable for veneers and furniture. An investigator went to a nearby sawmill, where he found a log matching the dimensions and appearance of one of the stumps, but wanted to be sure.

  8. Ironstone - Wikipedia

    en.wikipedia.org/wiki/Ironstone

    Ironstone (sandstone with iron oxides) from the Mississippian Breathitt Formation, Mile Marker 166, I-64, Kentucky. Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially.

  9. Hardboard - Wikipedia

    en.wikipedia.org/wiki/Hardboard

    Hardboard is similar to particle board and medium-density fiberboard, but is denser, stronger and harder because it is made out of exploded wood fibers that have been highly compressed. [ 3 ] The density of hardboard is higher than 500 kg/m 3 (31 lb/cu ft), [ 4 ] usually about 800–1,040 kg/m 3 (50–65 lb/cu ft). [ 5 ]