Farm system boundaries: Discussion of system boundaries in Chapter 3 mainly relates to farms of this type. Briefly, boundaries of Type 2 farm systems (and of Types 1, 3 and 4) segregate them distinctly from the external world, but the boundaries between individual farms are relatively weak.
What is Chromium? Chromium is a steel-gray lustrous metal that is important as an additive in the manufacture of steel alloys (chrome steel, chrome-nickel steel, stainless steel) and greatly increases the durability and resistance of these metals; hence its use in metal prosthetic implants.
Chromium is found mainly in chromite. This ore is found in many places including South Africa, India, Kazakhstan and Turkey. Chromium metal is usually produced by reducing chromite with carbon in an electric-arc furnace, or reducing chromium(III) oxide with aluminium or silicon.