Just saw these guys too.   As someone that HAS been scammed this site is triggering red flags for me.

After reviewing the results here:
https://www.scamadviser.com/check-website/altmininggear.com

Then looking at Whois info

   Domain Name: ALTMININGGEAR.COM
   Registry Domain ID: 2146524103_DOMAIN_COM-VRSN
   Registrar WHOIS Server: whois.namecheap.com
   Registrar URL: http://www.namecheap.com
   Updated Date: 2017-11-19T18:42:41Z
   Creation Date: 2017-07-24T20:23:37Z
   Registry Expiry Date: 2018-07-24T20:23:37Z
   Registrar: NameCheap Inc.
   Registrar IANA ID: 1068
   Registrar Abuse Contact Email:
   Registrar Abuse Contact Phone:
   Domain Status: clientTransferProhibited https://icann.org/epp#clientTransferProhibited
   Name Server: DNS1.NAMECHEAPHOSTING.COM
   Name Server: DNS2.NAMECHEAPHOSTING.COM
   DNSSEC: unsigned
   URL of the ICANN Whois Inaccuracy Complaint Form: https://www.icann.org/wicf/
>>> Last update of whois database: 2017-11-22T21:57:49Z <<<


These guys opened shop 2 mothers ago and updated their information 3 days ago.  Red Flag
I can only assume their update was to enable the WhoisGuard Protection (RedFlag) so we can't get their personal contact information.
Since the first link show the site hosted in the UK that seems very strange for a US company to host in the UK.  Not completely out of the question but there that puts them outside US laws.   Red Flag.

So there are 3 red flags and as they say in Baseball 3 strikes and your out.

Best wishes.