Final answer:
Enclosed spaces, small impurities, and the presence of water can impede a mineral from developing its natural crystal form, or habit, by creating defects and preventing perfect lattice formation.
Step-by-step explanation:
The question pertains to what discourages minerals from achieving their natural crystal form or "habit." Among the options, enclosed spaces, small impurities in the crystal structure, and the presence of water can potentially impede a mineral from achieving its perfect crystalline form. If a mineral forms in an enclosed space, it may not have the room to grow to its full potential, leading to distorted habits. Small impurities within the crystal structure can introduce distortions and create defects such as vacancies or interstitial sites, which can prevent the crystal from forming a perfect lattice. Similarly, the presence of water can affect a mineral's ability to achieve a perfect habit, especially if the attraction between ions and water molecules is weak, which could prevent the dissolution of minerals like calcium carbonate, calcium phosphate, and iron oxide. It's important to note that sufficient time to form and chemical composition are actually requirements for the proper formation of a mineral's crystal habit, rather than factors that discourage it.