"By-product" means any mineral or minerals, exclusive of oil, hydrocarbon gas, helium or other hydrocarbon substances, which are found in solution or in association with geothermal resources, and which have a value of less than seventy-five percent of the value of geothermal resources or are not, because of quantity, quality or technical difficulties in extraction and production, of sufficient value to warrant extraction and production by themselves.
(Ord. MC-298, 8-17-83)