Quartz Family · common

Milky Quartz

Milky quartz is the cloudy white to grayish-white variety of quartz, SiO2, its characteristic opacity caused by countless microscopic fluid inclusions and tiny gas bubbles trapped during crystal growth. It is the most common form of macrocrystalline quartz found in veins worldwide, forming wherever silica-saturated hydrothermal fluids cool and crystallize within fractures in host rock. Unlike clear rock crystal quartz, milky quartz's cloudiness comes specifically from these internal inclusions rather than from any difference in chemical composition.

Photo: University of South Carolina. McKissick Museum · Wikimedia Commons · CC BY 4.0

Milky Quartz properties at a glance

Type	Quartz Family
Chemical formula	SiO2
Mohs hardness	7
Crystal system	Trigonal
Luster	Vitreous, greasy
Streak	White
Cleavage	None
Fracture	Conchoidal
Specific gravity	2.65
Transparency	Translucent to nearly opaque
Common colors	Milky white, White
Rarity	common

Geology & background

Milky quartz forms when silica-rich hydrothermal fluids, often tied to granite intrusions or regional metamorphism, fill fractures and cavities in host rock and crystallize quickly, trapping abundant microscopic fluid and vapor inclusions that scatter light and produce the mineral's characteristic cloudy white appearance. It occurs essentially worldwide wherever quartz veins form, with notable large-scale deposits in the Appalachian Mountains, the Alps, Brazil's pegmatite regions, and countless other vein systems, making it one of the most abundant minerals collectors will encounter. Quartz veins hosting milky quartz frequently also carry gold or tourmaline, making it a common visual guide for prospectors tracing mineralized structures.

Because milky quartz is so common, individual specimens are generally valued more for size, crystal form, and included minerals than for rarity. Rockhounds often encounter large, blocky masses or clusters of stubby hexagonal prisms, and specimens showing well-formed terminations or included minerals like rutile needles or pyrite crystals stand out from the abundant plain vein material typically found in stream gravels and quarry tailings.

How to identify Milky Quartz

Milky quartz is white to grayish-white and translucent to nearly opaque, with a vitreous to slightly greasy luster and a white streak. It has quartz's characteristic hardness of 7, no cleavage, and a conchoidal fracture, typically occurring as massive vein material or as hexagonal prismatic crystals with pyramidal terminations. It can be distinguished from calcite, which is much softer and effervesces in acid, and from other white minerals by its hardness and glassy fracture surfaces; its cloudy appearance separates it from clear rock crystal quartz, though both share identical chemistry.

Compare the specimen's color, luster, crystal habit, grain size, streak, and locality before confirming.
Use multiple photos when possible, including a fresh surface and a close view of texture.

Where Milky Quartz is found

Reported from multiple localities worldwide; verify locality against specimen provenance when available.

How much is Milky Quartz worth?

Entry-level specimen	$5
Typical collector specimen	$35
Premium specimen	$250+

Value depends on size, crystal quality, color, locality, rarity, damage, and provenance.

Common uses

Collector specimens
Display
Education
Lapidary work when suitable

Interesting facts

The milky white color comes from thousands of microscopic fluid and gas inclusions trapped during rapid crystal growth, not from any impurity in the silica itself.
Prospectors historically used exposed milky quartz veins as visual guides for tracing gold-bearing structures underground, since gold often deposits alongside quartz in the same hydrothermal systems.
Quartz is piezoelectric, generating a small electrical charge when compressed, a property discovered in quartz crystals including common varieties like milky quartz before being engineered into modern electronics.