Zenite
Zenite was a mineral that was useful in countering plant diseases. It was found only on Ardana in soft ore material, and hand removal was the preferred method of mining. 

However, the Ardanans were apparently unaware that the mineral in its raw state had an undesirable byproduct: it emitted a colorless and odorless gas that temporarily impaired synaptic functions, stunting the subject's intelligence and emotional control. When the subject was removed from a high concentration of the gas, brain functions returned to normal. This medical problem was discovered by Dr. Leonard McCoy, who also learned that a simple filter mask was sufficient to prevent exposure. 

In 2269, the  requested a consignment of zenite to treat the botanical plague on Merak II. Upon arriving to pick up the zenite, they became involved in a dispute with the Troglyte miners and the inhabitants of Stratos. 

Both sides were reluctant to accept these claims, and only after concerted diplomatic efforts did they agree to take prescribed safety precautions for mining. ()

External link
 

de:Zenit
Drugs