What is the meaning of "Quartz contentment" in the poem, After Great Pain, a Formal Feeling Comes?

The "Quartz contentment" to which the speaker refers in the second stanza symbolizes the ambivalent nature of grief. The word "quartz" denotes a hard, stony exterior, which suggests a sense of entrapment for the person going through the post-traumatic experience. However, "contentment" suggests a sense of comfort and familiarity. Ultimately, the phrase figures the experience of grief as a type of temporary but necessary numbness.