Cannot reliably copy to SDCX

Question

I have 2 new 256gb Micro-SDXC cards, each from a different manufacturer.  My attempts to copy files from either my laptop SSD or from a USB FIT drive are inconsistently failing.  The result is that Windows appears to be copying the files (and certainly taking an extreme length of time to complete the copy), but often the folder on the SDXC card is empty.  

I am having success by first creating the folder on the SDXC card and then copying individual files into that folder; but cannot copy an entire folder to the SDXC card.

Additionally, the cards are rated for high speed transfer - Class 10 with a write speed up to 90 MB/s; Windows is showing the copy speed to be in the range of 600-800 GB/s, achieving less than 10% of anticipated speed.

I have tried attached the SDXC cards to my computer three different ways, all with the same results: (1) inserting the Micro-SDXC card into an adapter and then inserting the adapter into the SD slot of my Dell laptop, (2) inserting the Micro-SDXC card into an adapter and then inserting the adapter into a Memory Card reader which is plugged into a USB slot, and (3) inserting the Micro-SDXC card directly into the Memory Card reader which is plugged into a USB slot.

I am running Windows 10.  When I test the driver for the SD slot, I am told that the driver is up-to-date.

Answer 1

I did some more testing and I have found that I can not format an UN-formatted SD card.  I even tried EaseUS Partition Manager.

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Answer 2

Having 2 SD cards I did some testing.  I was able to use one and not the other.

The problem was that the second one was not formatted and I could not get it formatted with any one of my Windows 10 computers.

The one that was formatted worked.  It is formatted as Fat32.

I was able to transfer 2 full folders.  Not that big on the first one.  The second one I had to change the location of the folder to be copied as it was trying OneDrive which I do not use.