The utilization of a huge amount of waste generated from mining industries is vital for the sustainable and eco-friendly design of construction projects such as roads, embankments, and buildings. The World’s largest marble production, i.e., Rajasthan state of India is producing approximately 95% of the total marble in the country. The unscientific disposal of about 70% of marble waste (i.e., 15–20 lac tons) generated from 4000 marble mines in Rajasthan poses a major environmental threat due to its suspension in the air, increase in alkalinity of soils, water logging due to the reduction in porosity of the topsoil, etc. Marble dust (MD) has several advantageous properties such as coarser-sized particles, high shear strength (friction angle up to 44°), and non-plastic behavior which are alike with sand. Further, depletion of natural sand has forced to find suitable alternative material for its application as a geomaterial. Despite its unique characteristics of marble dust, the proper attempt has not been made to investigate the suitability of marble dust to be used alone or amendment with other additives such as bentonite (B), chemical stabilizers, etc. for geotechnical projects. The preliminary objective of present work is to find out its potential to be used in subgrade soil preparation. Detailed geotechnical investigations such as physical and engineering properties, physicochemical examination (pH and electrical conductivity) and microanalyses (mineralogical and microstructural) have been investigated in order to determine optimize the MD content for soil improvement. The secondary objective of the present work has been aimed to examine the effectiveness of marble dust amended with bentonite to be used as a landfill liner material in the substitution of sand–bentonite (S–B) mix. The geotechnical properties (i.e., swelling percentage and permeability) of MD–B mixes that are required to satisfy landfill liner design and construction are compared with S–B mixes. It is well known that the objective of engineered landfill liners is to control the migration/leakage of hazardous leachate solutions generated from dump wastes into the groundwater. Also, the interaction of liner material with hazardous leachates may lead to the alteration in the desired properties. Hence, the effects of electrolyte solutions (NaOH and NaCl) of various concentrations on the behavior of optimized MD–B mixes are investigated to confirm the efficacy and longevity potential to be used as an alternative to S–B mixes in landfills liner. Mechanisms of alteration in the properties of both mixes subjected to electrolyte concentration are brought out clearly through physicochemical and microanalyses.