Actually CME is using
CME CF Bitcoin Reference Rate for daily settlement and
CME CF Bitcoin Real-Time Index for marking to market during the day (basically the same methodology, par some details).
CME CF Bitcoin Reference Rate & CME CF Bitcoin Real-Time Index
CME CF Bitcoin Reference Rate (BRR) and CME CF Bitcoin Real-Time Index (BRTI), a standardized reference rate and spot price index with independent oversight are accelerating the professionalization of bitcoin trading. CME CF Crypto Currencies Indices have been generating BRR and BRTI rates since November 2016 with several bitcoin exchanges and trading platforms providing pricing data, including Bitstamp, Coinbase, Gemini, itBit, and Kraken.
So Gemini is only one of the 5 venue used to compute an average whose value is used to settle the future.
Chicago Board of Exchange (CBoE) is a different futures provider than the Chicago Mercantile Exchange (CME)
Sorry, I totally misread your statement.
Yes, CBoE used to trade bitcoin futures until March 2019, when they shut down because they attracted tiny volumes compared to CMEs future.
Actually on the CBoE website I now see a BTCH0 future, and I am quite puzzled.
News about closure at CBoT
https://www.cnbc.com/2019/03/18/cboe-to-stop-listing-bitcoin-futures-as-interest-in-crypto-trading-cools.htmlEDIT: the only explaination I have for this is that they decided to stop listing new series of bitcoin futures right after they started quoting the XBTHO (H0 means expiring March 20) that at the time was maturing in one year. Open Interest is neglibile. This is why I didn't think about CBoE, but yes alyssa85, you are technically right.