Consolidated revenues for the quarter ended July 31, 2021 were $133.0 million, which represented an increase of $45.5 million, or 52.0%, from consolidated revenues of $87.5 million reported for the three months ended July 31, 2020. The increase was primarily due to increasing revenues at Gemma Power Systems associated with the ongoing construction of the Guernsey Power Station and the initial construction activities on the Maple Hill solar energy facility which began in May 2021. The combined revenues associated with these two projects represented 67.3% of consolidated revenues for the three months ended July 31, 2021. Additionally, revenues at The Roberts Company, our industrial fabrication and field services segment, increased by $13.5 million, or 80.7%, to $30.2 million for the period compared to revenues of $16.7 million for the three months ended July 31, 2020. Our businesses were adversely impacted by the COVID-19 outbreak during the three months ended July 31, 2020; the effects were minimized during the current quarter.
Consolidated gross profit for the three-month period ended July 31, 2021 was $27.7 million, which is primarily a reflection of increased consolidated revenues. The gross profit percentages of corresponding revenues for the power industry services, industrial services and the telecommunications infrastructure segments were 20.7%, 20.9% and 21.8%, respectively, for the quarter ended July 31, 2021.
Selling, general and administrative expenses for the three months ended July 31, 2021 and 2020 were $10.3 million, or 7.8% of corresponding consolidated revenues, and $9.1 million, or 10.4% of corresponding consolidated revenues, respectively.
Due primarily to the consolidated pre-tax book income reported for the three-month period ended July 31, 2021 in the amount of $17.1 million, we reported income tax expense in the amount of $4.2 million, which represents an effective income tax rate of 24.6% for the period. For the three-month period ended July 31, 2020, we recorded an income tax expense of $1.4 million which represented an effective income tax rate of approximately 20.0% for the three-month period.
For the three months ended July 31, 2021, our improved overall operating performance resulted in net income attributable to our stockholders in the amount of $12.9 million, or $0.81 per diluted share, compared to $5.6 million, or $0.36 per diluted share, in the prior year quarter.
For the six months ended July 31, 2021, our improved overall operating performance resulted in net income attributable to our stockholders in the amount of $23.6 million, or $1.48 per diluted share, compared to $4.8 million, or $0.31 per diluted share, in the prior year period.
As of July 31, 2021, cash, cash equivalents and short-term investments totaled $491 million and net liquidity was $290 million; furthermore, the Company had no debt. The Company’s consolidated amount of RUPO was approximately $0.5 billion as of July 31, 2021.
About Argan, Inc.
Argan’s primary business is providing a full range of services to the power industry, including the renewable energy sector. Argan’s service offerings focus on the engineering, procurement and construction of natural gas-fired power plants and renewable energy facilities, along with related commissioning, operations management, maintenance, project development and consulting services, through its Gemma Power Systems and Atlantic Projects Company operations. Argan also owns The Roberts Company, which is a fully integrated fabrication, construction and industrial plant services company, and SMC Infrastructure Solutions, which provides telecommunications infrastructure services.