silicates
Schorl
NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH)
- Also known as
- black tourmaline
- Crystal system
- trigonal
- Hardness
- 7–7.5 on the Mohs scale
- Lustre
- vitreous
- Colour
- Black
- Where it forms
- In granites, pegmatites and metamorphic rocks. It is common enough to be a rock-forming mineral in some settings.
- Chiefly from
- worldwideBrazilPakistanNamibia
Why it is that colour
Iron. Schorl is the iron tourmaline and it accounts for the overwhelming majority of all tourmaline in the earth’s crust.
Safety
Safe to handle.
Where it comes from
Extremely abundant and very cheap. Sold in enormous volume as raw chunks and tumbled stones.
Historical use
For most of the history of mining, schorl was waste — a black mineral that got in the way of tin extraction in Cornwall and Saxony.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
The name comes from a Saxon mining village and appears in German sources from the fifteenth century, but as a miner’s term for an unwanted mineral rather than as anything symbolic. Its current reputation as the principal stone of psychic protection, and specifically as a shield against electromagnetic radiation, is New Age with an internet-era extension.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Worth knowing
Black tourmaline is now among the highest-volume stones in the wellbeing trade, sold chiefly for protection against electromagnetic fields and, since about 2019, against 5G specifically.
The claim rests on the pyroelectric and piezoelectric properties, which are real, and on a leap that is not. A mineral that develops a small static charge when heated or squeezed does not attenuate radio frequency radiation, and nothing sitting beside a router alters what the router emits. There is also nothing to shield from: non-ionising radio-frequency fields at consumer power levels have been studied extensively and there is no established mechanism or evidence of harm.
Its original name was a term of contempt. Saxon miners called it schorl because it was the black stuff cluttering the tin.
Identity checked against IMA-CNMNC master list, June 2025.