Adamant

[Todd]

This reminded me of the story of Jesus and the woman breaking the alabaster box over him releasing the nard. Maybe she was Mary Magdalene (I think that's general church tradition). You chose a versatile title. This could be either the verb something unyielding (kingdom that cannot be shaken, an overcomer against persecution). Also, the noun, the substance which could tie this into a statue, an icon, a means to stimulate worship. It could also stand as a metaphor for perseverance under adversity.

she wears the holes of crucifixion--evocative first line. I get an early church Galatians 2:20 read along with the physical idea of maybe something being drilled into the hands of a statue to hold an object.
from the years spent standing in place of a cock--This does a little more than identify the position of the "she". It isn't just that like a weathervane, she's on the top of the building. She stands in place of a cock. Taking a position usually reserved for a man. Patriarchy ideas. This again, could largely be an image fueling the metaphor.
at the mercy of the winds that swirled across the steeple--the winds could be contrary opinion on morality or orthopraxy. It could be a way of saying that lives get affected by powers, people, and institutions beyond themselves.
 
now fallen, her wings are torn from her back--This could be a broken angel statue, the idea of original sin, or perhaps a look into Mary Magdaline's past. It could also be the speaker reflecting on their identification with those ideas.
and her breast is exposed from behind--so, she like Christ was also pierced through and from behind--implying surprise and betrayal.
so her traitor heart can pump its last---Traitor heart seems more of an accusation leveled than a self-identity.
into the filth upon which this church perches--The foundation is corrupt.
like an aged buzzard--The church as carrion. The church as roadkill.
too blind to do more than peck feebly for bile--the key is blindness. Like the Pharisees who tithe mint and dill and cumin but neglect mercy and justice. Like the winds, they blow their victims without mercy.
 
beneath her hand, the shards of a once-sealed jar--This was where I get the alabaster jar. It is once sealed, but it's treasure was released. This is a person who poured herself out as an offering.
stab at her skin, and within its shattered curve--Curve gives a feminine reading to the line. The speaker is the shattered jar in some sense.
is a single white feather--This is a hopeful image. A reminder of the lost wings.

I'm sure I was all over the place. I enjoyed the read, Leanne.

Best,

Todd