Answers to the Mineral lab Pre-quiz

What is the difference between streak and color? Why do we bother with both?

"Color" denotes the color of the hand specimen, which might consist of crystals of different size and form, all of which can affect its macroscopic color.

"Streak" describes the color of a fine crystalline powder (that is produced by scratching the specimen against a porcelain plate). Since the crystal size is better controlled than in the hand specimen the color may be more consistent and more diagnostic.

Will quartz scratch the surface of your (steel) geology hammer?

Check the book, it will tell you that quartz has a Mohs hardness of 7, which is harder than steel, which has a Mohs hardness of 5.5 to 6 (depending on the type of steel). With quartz being harder than steel, it will scratch the hammer.