Faden Quartz Identification Guide
Identify Faden quartz by the white thread-like line running through tabular crystals, plus standard quartz tests and its alpine-cleft origin.
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What Faden Quartz Looks Like
Faden quartz (German Faden = "thread") is quartz containing a distinctive white, fibrous-looking line or thread that runs through the crystal. The thread marks where a crystal repeatedly cracked in a slowly opening fracture and self-healed, growing outward from the line.
- Color: usually colorless to milky/white; the thread is opaque white.
- Luster: vitreous.
- Transparency: transparent to translucent body with an opaque white line.
- Habit: typically flattened/tabular crystals or crystal groups grown in two directions away from the central thread; often doubly terminated.
Step-by-Step Field-ID Checklist
- Find the thread. Look for a single, slightly zigzag white line stretching across or through the crystal.
- Note the tabular growth. Crystals tend to be flattened and grow symmetrically outward from the thread.
- Confirm quartz. Hexagonal prism faces, glassy luster, scratches glass (Mohs 7).
- Check terminations. Faden specimens are often doubly terminated (points at both ends).
- Backlight it. The thread appears as a fibrous bright line within otherwise clear quartz.
Key Diagnostic Tests
- Mohs hardness: 7 (scratches glass, not scratched by a steel knife).
- Streak: white.
- Cleavage/fracture: none; conchoidal fracture.
- Specific gravity: ~2.65.
- The thread structure is the defining visual diagnostic rather than any chemical test.
- No acid reaction, no magnetism.
Common Look-Alikes and How to Tell Them Apart
- Ordinary milky quartz with a white streak inclusion: the Faden thread is a continuous fibrous line tied to tabular two-sided growth; random milky patches are not.
- Rutilated quartz: contains golden/red needle inclusions, not a single white thread.
- Phantom quartz: shows ghost outlines of earlier crystal faces, not a linear thread.
- Glass: has bubbles, no hexagonal form, warmer to the touch, and is scratched by quartz.
- Calcite/selenite tabular crystals: much softer (3 and 2), and calcite fizzes in acid.
Where It Is Typically Found
Faden quartz forms in alpine-type fissures and cracks that slowly pull apart in tectonically active rock. The best-known specimens come from the Himalaya (Pakistan, especially the Baluchistan and northern areas), as well as the European Alps, Morocco, and other orogenic belts. The thread records the gradual opening of the host fracture.
Frequently asked questions
What is the white line in Faden quartz?
It is the 'Faden' (thread): a fibrous white zone marking where the crystal repeatedly cracked in a slowly opening fissure and healed itself, with new quartz growing outward from the line.
How can you tell if it's real Faden quartz?
Look for a continuous white thread running through a flattened, often doubly terminated quartz crystal, with hardness 7, glassy luster, white streak, and conchoidal fracture. The threaded tabular growth is the key identifier.
Why is Faden quartz often flat or tabular?
The crystal grows sideways in two directions away from the central thread inside a thin, slowly widening fracture, which constrains it into a flattened, tablet-like shape.
Faden quartz vs rutilated quartz: how do they differ?
Faden quartz contains a single white fibrous thread tied to tabular growth, while rutilated quartz contains scattered golden or reddish needle-like rutile crystals. The inclusion type and crystal shape distinguish them.