
1) Manganese mineral
Found on
https://www.crosswordclues.com/clue/knebelite

Knebelite is a silicate mineral, a manganese variety of fayalite with formula (Fe,Mn)2SiO4. It forms dark green orthorhombic crystals. It is reported from a variety of locations in Sweden as well as South Africa, Russia, British Columbia, New Hampshire, and Rhode Island. ...
Found on
http://en.wikipedia.org/wiki/Knebelite

• (n.) A mineral of a gray, red, brown, or green color, and glistening luster. It is a silicate of iron and manganese.
Found on
http://thinkexist.com/dictionary/meaning/knebelite/

(from the article `olivine`) ...is soluble in all proportions with ash-gray tephroite (from Greek tephros, `ashen`), pure manganese silicate (Mn2SiO4); the intermediate in the ... Knebelite olivines are restricted to iron-manganese ore deposits, to their associated skarn (lime-bearing silicate rocks) zones, and to metamorphose...
Found on
http://www.britannica.com/eb/a-z/k/40
Kne'bel·ite noun [ From Major von
Knebel .]
(Min.) A mineral of a gray, red, brown, or green color, and glistening luster. It is a silicate of iron and manganese.
Found on
http://www.encyclo.co.uk/webster/K/14

Knebelite, named after Major von Knebel, is a mineral of a grey, red, brown, or green colour, and glistening lustre. It is a silicate of iron and manganese.
Found on
http://www.probertencyclopaedia.com/browse/HK.HTM
No exact match found.