Milky Quartz
Silicon dioxide (SiO2)
The most common variety of quartz, milky white from microscopic fluid and gas inclusions, forming massive veins worldwide.
- Mohs hardness
- 7
- Color
- Cloudy white to milky translucent
- Type
- crystal
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Overview
Milky quartz is the most common variety of crystalline quartz, named for its cloudy, milk-white appearance. It forms enormous masses and veins and is often the white quartz seen weathering out of hillsides and stream beds.
The milkiness results from large numbers of tiny fluid and gas inclusions trapped during crystal growth, which scatter light. Some specimens grade from milky bases into clearer terminations.
While abundant and inexpensive, it is significant geologically and historically, frequently serving as the host (gangue) rock for gold deposits.
Formation & geology
Milky quartz precipitates from silica-saturated hydrothermal fluids filling fractures, faults, and cavities, creating quartz veins. It also forms in pegmatites and as a primary mineral in many igneous and metamorphic rocks.
The abundant inclusions form when crystals grow under conditions of rapid precipitation or changing pressure and temperature, sealing in water and gas.
Milky quartz is globally ubiquitous; prominent examples come from Brazil, Madagascar, the United States (Appalachians and the West), and gold districts worldwide where it carries economic mineralization.
How to identify it
Identify by cloudy white color, hardness of 7 (scratches glass), glassy fracture surfaces, and a white streak. It has no cleavage and shows conchoidal fracture.
When crystals are present they are six-sided prisms with pyramidal tips. Most milky quartz, however, is massive and vein-like.
Look-alikes: Calcite and marble are much softer and react with acid; feldspar shows cleavage planes and is slightly softer; barite is much heavier and softer. The combination of hardness 7, no cleavage, and conchoidal fracture is diagnostic for quartz.
Uses & significance
Milky quartz is used as a lapidary and decorative material for beads, tumbled stones, and carvings, and is sometimes crushed for landscaping and aggregate. High-purity vein quartz is a source of industrial silica for glass and ceramics.
Its greatest economic importance is as the classic host rock of lode gold; prospectors have long followed milky quartz veins seeking gold.
Metaphysically it is regarded as a gentle, nurturing form of quartz associated with calm and clarity, a spiritual rather than scientific attribution.
Frequently asked questions
Why is milky quartz cloudy?
It contains abundant microscopic fluid and gas inclusions that scatter light, giving it a milky white look instead of transparency.
Is milky quartz worth anything?
It is very common and low in monetary value, but it is valued decoratively and historically as the host rock for many gold deposits.
Does milky quartz contain gold?
Some milky quartz veins do host gold, which is why prospectors examine them, but most milky quartz contains no gold at all.
What is the difference between milky quartz and snow quartz?
They are essentially the same material; "snow quartz" is largely a trade name for opaque white milky quartz used in jewelry.
Milky Quartz guides
In-depth guides for identifying, valuing, and understanding Milky Quartz.
Milky Quartz identified by the community
Real specimens identified with Rock Identifier.
