Nanotesla - The international unit for measuring magnetic flux density. Native metal - A metal occurring in nature in pure form, uncombined with other elements, Net profit interest - A portion of the profit remaining after all charges, including taxes and bookkeeping charges, such as depreciation, have been deducted. Net smelter return - A share of the net revenues generated from the sale of metal produced by a mine. Net worth - The difference between total assets and total liabilities. Norite - A coarse-grained igneous rock that is host to copper/nickel deposits in the Sudbury area of Ontario, Nugget - A small mass of precious metal, found free in nature. Odd lot - A block of shares that is less than a board lot. Open order - An order to buy or sell stock, which is good until canceled by the client. Open pit - A mine that is entirely on surface. Also referred to as open-cut or open-cast mine. Option - An agreement to purchase a property reached between the property vendor and some other party who wishes to explore the property further. Option (on stock) - The right to buy or sell a share at a set price, regardless of market value. Ore - A mixture of ore minerals and gangue from which at least one of the metals can be extracted at a profit. Ore pass - Vertical or inclined passage for the downward transfer of ore connecting a level with the hoisting shaft or a lower level. Orebody - A natural concentration of valuable material that can be extracted and sold at a profit. Ore Reserves - The calculated tonnage and grade of mineralization which can be extracted profitably; classified as possible, probable and proven according to the level of confidence that can be placed in Oreshoot - The portion, or length, of a vein or other structure that carries sufficient valuable minerals to be extracted profitably. Organic maturation - The process of turning peat into coal. Orogeny - A period of mountain-building characterized by the folding of a portion of the earths crust. Outcrop - An exposure of rock or mineral deposit that can be seen on surface, that is, not covered by soil or water. Overturned - Where the oldest sedimentary rock beds are lying on top of a younger beds. Oxidation - A chemical reaction caused by exposure to oxygen that results in a change in the chemical composition of a mineral.   Prospecting &  Mining Basics