Note 7.  Property and Equipment

Property and equipment consisted of the following as of December 31, 2019 and 2018 (in thousands): 

There were no impairment charges related to miners for the year ended December 31, 2019. The breakdown of the impairment charges recorded for the year ended December 31, 2018 are as follows (in thousands):

During December 2019, the Company purchased 4,000 next generation Bitmain S17 Pro Antminers for approximately $6.3 million from Bitmain. In December 2019, 3,000 miners had been received at the Company’s Oklahoma City facility but not yet placed in service.

The remaining 1,000 miners were received at its Oklahoma City facility during February 2020 and the related $1.4 million prepayment is recorded as a deposit on the accompanying consolidated balance sheet.

Depreciation and amortization expense totaled approximately $0.1 million (including $0.09 million of patent amortization) and $5.2 million, for the years ended December 31, 2019 and 2018, respectively. Depreciation is computed on the straight-line basis for the periods the assets are in service.