Tests later confirmed it was the Class C controlled drug Benzylpiperazine (BZP).
At the roadside, Mariu told police everything inside the car was his own, however, later at the station he said the items had been in his car for some time and he didn't know what the substance was.
Defence lawyer James Elliott said Mariu used BZP as a way of dealing with his back problems. He said Mariu had also pleaded guilty at the earliest possible opportunity.
"Mr Mariu suffers from a spinal injury and, as a result, he suffers from spasms and tremors throughout his back," he said. "He finds that stimulants help him and, while I'm not offering it as an excuse, it is a reason why he used it."
Mr Elliott said Mariu was unemployed, however, he worked as a voluntary shearer from time to time.
Judge Michael Behrens also ordered Mariu to pay court costs of $132.89 and directed that the drugs be destroyed.