Crystal Quiz
Questions: 16 · 10 minutes
1. Why do well-formed snow crystals commonly display sixfold patterns?
The molecular arrangement of ordinary ice favors hexagonal symmetry
Air currents carve six matching arms into every snow crystal
Frozen water always develops six cleavage directions
Gravity divides each droplet into six equal sections
2. What feature most directly distinguishes a crystal from ordinary glass?
It is always transparent when held to light
Its atoms or molecules have a repeating, ordered arrangement
It must have naturally flat outer faces
It is composed of only one chemical element
3. Diamond and graphite are both made of carbon, yet they have very different hardness and appearance. What best accounts for this?
Their carbon atoms have different arrangements and bonding
Only diamond has atoms; graphite is a mixture
Graphite contains no crystalline structure
Diamond is hard only because it is transparent
4. A cooled material is solid and shiny but lacks long-range atomic order. How should it be classified?
As a crystal because all solids are crystalline
As an amorphous solid rather than a crystal
As a mineral because shininess proves crystallinity
As a crystal only if it is transparent
5. Amethyst is the purple variety of which mineral?
Halite
Calcite
Quartz
Gypsum
6. A freshly broken halite specimen tends to produce cube-like pieces. What best explains this pattern?
Halite always grows as a perfect cube without defects
Halite fractures randomly because it lacks internal order
Halite has a hardness identical to glass
Halite has three cleavage directions that meet at right angles
7. When clear calcite is placed over printed text, two images of the letters may appear. Which optical property causes this?
Fluorescence
Metallic luster
Double refraction
Streak
8. A mineral scratches calcite, which has Mohs hardness 3, but does not scratch quartz, which has hardness 7. What can you reasonably conclude?
Its hardness lies somewhere above 3 and below 7
Its hardness is greater than 7
Its hardness is exactly 3
Hardness cannot be compared by scratch testing
9. Inside a hollow rock cavity, crystals point inward from the walls. How did this geode lining most likely form?
The crystals were pushed into the cavity by pressure
Mineral-rich fluid entered the cavity and deposited crystals over time
Loose crystal fragments became glued to the cavity wall
The hollow space melted while the outer rock stayed solid
10. Which chemical formula belongs to quartz?
CaCO₃
Al₂O₃
NaCl
SiO₂
11. A hot solution contains as much dissolved material as it can hold. As it cools slowly, crystals begin forming. Why?
Cooling removes the repeating structure from the solid
The container turns dissolved material into a new element
Every liquid automatically freezes into mineral crystals
The solution can hold less dissolved material, allowing excess material to crystallize
12. An opaque metallic-looking mineral has a surface altered by weathering. Which test could reveal the color of its powdered form?
Checking its crystal habit
Holding it against a printed page
Rubbing it on an appropriate unglazed porcelain streak plate
Placing it in water to observe bubbles
13. A laboratory-grown quartz crystal has the same composition and ordered structure as natural quartz. Which statement is most accurate?
It cannot be a crystal because people helped produce it
It is glass because all laboratory solids are amorphous
It becomes quartz only after weathering outdoors
It is quartz produced under controlled conditions rather than by a natural geological process
14. What is crystal twinning?
Two unrelated minerals that happen to have the same color
An intergrowth of crystals joined in specific, symmetry-related orientations
A crystal containing equal amounts of two elements
A specimen that breaks into two identical fragments
15. In mineralogy, what does crystal habit describe?
The temperature at which a mineral melts
The color of a mineral in powdered form
The characteristic external shape or growth form of a crystal
The way light splits inside every transparent mineral
16. A mica specimen repeatedly separates into smooth, thin sheets. Which property are you observing?
Cleavage
Luster
Conchoidal fracture
Streak