How to tell one mineral from another
1 min 49 s. The words are spoken and shown in the picture; the player can also show them as subtitles.
For the Earth and Space Sciences Regents. Topic: Mineral identification, with the past questions on it.
What Dr. Mars says (the words of the video)
How do you tell one mineral from another?
A mineral is identified by testing its properties.
This mineral is steel-gray and shines like metal.
This shine is called a metallic luster.
Dr. Mars rubs it on a streak plate.
Its powder is red-brown, not steel-gray.
Streak is the color of a mineral's powder.
A mineral's color can vary from sample to sample.
Streak is a better test than color.
Next, he scratches a glass plate with quartz.
Quartz scratches glass, so it is harder than glass.
On the Mohs Hardness Scale, quartz is seven and glass is five point five.
Now he uses the Mineral Identification Flowchart.
Metallic luster and a red-brown streak: hematite.
Hematite can be steel-gray or red-brown in color.
Quartz's path: harder than glass, then poor or no cleavage.
Cleavage is splitting along flat, smooth surfaces.
They reflect light like polished glass.
These surfaces form along planes of weak bonds between atoms.
Check yourself! A steel-gray mineral has a red-brown streak. Which is it: A, B, or C?
Look at the streak, not the color.
Answer: C! Hematite has a red-brown streak.
Dr. Mars made this streak on his streak plate.
Dr. Mars. Free practice for the New York Earth and Space Sciences Regents.