Quartz Has a Characteristic Conchoidal Fracture, Yet Rock Shops Often

question 86

Multiple Choice

Quartz has a characteristic conchoidal fracture, yet rock shops often sell quartz as elongate six sided objects with a pointed termination. What causes this shape?

• A) You should never buy a crystal like this because it is clearly fake, only artificial crystals grow this way.
• B) Quartz usually is amorphous, consistent with its conchoidal fracture, but when it grows it grows against minerals with planar faces, causing this shape.
• C) The rock shop cuts them that way with abrasives. The facets are cut to give the crystals more "power" for the crystal people.
• D) The planar faces that form the object are crystal faces that grow when the crystals grew into a void.

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Definitions:

Iris

The colored part of the eye that controls the size of the pupil and thus the amount of light that enters the eye.

Light Entry

The process or manner by which light enters an area or passes through a medium.

Young-Helmholtz Theory

A theory of color vision that proposes the presence of three types of color receptors in the eye, each sensitive to red, green, or blue light.

Red-Sensitive

Red-sensitive refers to the capacity of certain cells in the retina, called cones, that are especially responsive to red light, playing a key role in color vision.