|MadSci Network: Physics|
Dear User, Generally speaking, the crystals that appear in nature and those that you are going to produce artificially would not be very different. In many cases, crystals are affected by the environment in which they grow, however in the case of NaCl and MgSO4 you would not necessarily be able to observe any differences other than those based on purity of the crystals. NaCl can be crystallized in several 'habits' (crystal shapes) however it would take some fiddling to obtain them, and natural Halite is just cubic NaCl of the same sort you'd grow via evaporation of saturated solution. You can add certain substances, such as amino acids, to NaCl solution to induce growth of octahedral-looking crystals (there's a very old reference in one of the scientific journals but I can't say I remember the details). In general, if you were to experiment with crystal growth, I'd suggest to study effects that other substances would have on crystallization of some sort of common inorganic salt. You may stumble on something interesting or even something unknown. Best regards, A.G.E.
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