Gravel, often used as a coarse aggregate, has a hardness that depends on the types of rocks included, generally ranging from 6-7 on the Mohs scale. The type of diamond core bit used must correspond to the hardness of the aggregate. For harder aggregates like granite, soft bond type ...
Turquoise is almost always cryptocrystalline and huge and requires no clear internal form. Crystals are exceedingly uncommon even on a microscopic scale. Typically the shape is in habit of filling vein or fracture, nodular or botryoidal. Forms of stalactitis were recorded. Feldspar, apatite, oth...
When striking your flint of metal, make sure the stone is dry, as a damp stone may not produce sparks. Other rocks, such as quartz, that have a hardness of seven on the Mohs Scale of Hardness will create sparks when struck against a carbon metal. If you are only looking for a rock...