Transparency
Definition
The degree to which light passes through a mineral. Minerals can be transparent (clear), translucent (some light passes through), or opaque (no light passes through).
Example
Clear quartz is transparent, while rose quartz is translucent, and hematite is opaque.
Light Transmission
Transparency describes the ability of a mineral to transmit light. It is distinct from color. A mineral can be black but transparent (like smoky quartz) or white but opaque (like milky quartz). This property often dictates whether a stone is faceted as a gem or cut as a cabochon.
Categories
- Transparent: Objects can be seen clearly through the stone (e.g., high-quality Diamond, Rock Crystal).
- Translucent: Light passes through, but objects look blurry or cloudy (e.g., Rose Quartz, Jade). This creates a glowing effect.
- Opaque: No light passes through, even on thin edges (e.g., Hematite, Turquoise, Malachite).
Factors Affecting Transparency
Inclusions, internal fractures, and chemical impurities can all reduce transparency. "Silky" stones often have thousands of microscopic needle-like inclusions that block light transmission.