Identifying minerals involves examining a range of physical and chemical properties that are characteristic of each mineral species (Australian Museum, n.d.a). These properties arise from the mineral’s internal atomic structure and chemical composition (USGS, n.d.b).
Color is often the first observed property, though it can be variable for many minerals like quartz, making it less diagnostic than for minerals with consistent colors such as azurite (blue) or malachite (green) (Australian Museum, n.d.b).
Luster describes how a mineral’s surface reflects light, categorized as metallic (e.g., galena) or non-metallic (e.g. vitreous/glassy like quartz, pearly like talc, or earthy) (Australian Museum, n.d.b).
Streak, the color of a mineral’s powder, is a more reliable indicator than body color, especially for metallic minerals (Australian Museum, n.d.b).
Hardness, a mineral’s resistance to scratching, is commonly measured using the Mohs scale, ranging from 1 (talc) to 10 (diamond) (Australian Museum, n.d.b).
Cleavage refers to how a mineral breaks along planes of weakness, described by the number and angles of these planes (e.g., mica has one perfect cleavage, calcite has three not at 90°). If a mineral breaks irregularly, it exhibits fracture (e.g., conchoidal fracture in quartz) (Australian Museum, n.d.b).
Crystal form or habit describes the typical external shape of mineral crystals, reflecting their internal atomic arrangement (Tulane University, n.d.).
Specific gravity (or density) is the ratio of a mineral’s weight to the weight of an equal volume of water (Australian Museum, n.d.b).
Special properties can also be diagnostic, such as magnetism (magnetite), reaction with dilute acid (calcite fizzes), taste (halite is salty), or fluorescence under UV light (Tulane University, n.d.).
Which mineral property do you think is the most reliable for identification and why?
