Basic color and shade are important. Exact hue is not always diagnostic because small impurities and weathering can greatly change the appearance of a mineral. Excellent example of this is the difference between rose quartz and smoky quartz. The first has small amounts of manganese while the latter has a carbon impurity. This works best for dark minerals.
Minerals can appear glassy, pearly, dull, metallic, etc .
Diamond is the hardest, talc the softest. To test hardness, see if the mineral can scratch common materials like fingernails, pennies, nails, glass, etc. When a drop of HCl touches calcite, carbon dioxide gas bubbles off from the chemical reaction between calcium carbonate and hydrochloric acid. Do not confuse with faces formed by breakage along cleavage lines. Test using material such as paper clips or compasses .