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When observing minerals without touching them, two physical properties that can be determined are luster and color. Let me explain:
1. Luster: This refers to how light reflects off the surface of a mineral. It can be categorized as metallic or non-metallic. For example, if a mineral reflects light like a metal, it has a metallic luster. If it reflects light like glass, it has a non-metallic luster.
2. Color: The visible hue of a mineral can be easily observed without touching it. Minerals can come in a variety of colors, and some minerals have characteristic colors that can aid in identification.
So, in the given options, the correct answer is "Luster and color" as the two physical properties of minerals that can be observed without touching them.
I hope this explanation helps you understand the concept better. If you have any more questions or need further clarification, feel free to ask!
