1 Cor. 10:4 - "that rock-mass meant the Christ" New World Translation

Despite the complaints about the NWT translating the Greek petra as "rock-mass", we see The New International Dictionary of New Testament Theology, Zondervan Publ., Vol. 3, p. 381, declaring that petra can mean "a mass of rock," and that this held true for the writers of the Septuagint (which was quoted in many places in the NT), p. 381.

And W. E. Vine tells us precisely that

"PETRA (petra) denotes a mass of rock, as distinct from petros, a detached stone or boulder, or a stone that might be thrown or easily moved." - An Expository Dictionary of New Testament Words, p. 974.

Vine also gives Matt. 16:18 as an example of petra used as a metaphor for Christ ["rock-mass"] which is contrasted with the metaphorical word-play petros ["rock" or "Peter"] for the Apostle Peter! (Compare the correct translation of Matt. 16:18 in the NWT with most other translations - also cf. Matt. 7:24.) Also notice the "strange" translations of petra at Matt. 27:60 in NAB (1970) and GNB!

"petra denotes a large `rock,' but also a `cliff' or `rocky mountain chain.' .... petros is more often used for smaller rocks, stones, or pebbles." - p. 834, Theological Dictionary of the New Testament, Kittel and Friedrich, abridged and translated by G. W. Bromiley, Eerdmans Publ., 1992 reprint.

We even find A. T. Robertson admitting in his discussion of Matt. 16: 18:

"On this rock … [petra] Jesus says, a ledge or cliff of rock like that in 7:24 on which the wise man built his house. Petros is usually a smaller detachment of this massive ledge." – p. 131, Word Pictures in the New Testament, vol. 1, Broadman Press.
And we have the following notes found in C.B. Williams' New Testament in the Language of the People and in the New American Standard Bible:

16:18 – "…your name from now on is to be Peter, Rock, and on a massive rock like this [note e] I will build my church" - Note e: `A different word from the word trans. Peter [petros]; i.e., petra, a massive rock, meaning faith in the Christ, the Son of God.'- CBW.

16:18 – "…you are Peter [note 1], and upon this rock [note 2] I will build My church" – Note 1: `Gr., Petros, a stone.' And note 2: `Gr., petra, large rock, bedrock.' – NASB, Reference Edition, Foundation Press, 1975.

Also see:

1 Cor. 10:4 - "that rock-mass meant the Christ" New World Translation (INDNWT)