Suminska surname. Is my Polish Grandmother a Jew?

In doing ancestral research I found my grandfather's (maternal side) mother name to be
Valeria Suminska or also spelled "Slominski". Is this a Jewish surname? Could she have been Jewish?

However, my grandfather Jan Zablocki (from Grodzanowo, Russia) married a Catholic polish woman - Sophie Ciezewska (from Raciaz Poland).

Any apparent Jewish heritage here? I have hit a roadblock and can not find further information. Any help is appreciated.

Thank you.

The names you mentioned are not Jewish names as such but could have been used by Jews -- most any name can and has been. Typically Jewish names are things like Aszkinazi, Halborn, Mojżesz, Model, Lewin, Margolis, Szapiro and the Prussian-imposed Rosenblum, Weingarten, Rubinstein, Perlmann, etc.

SUMIŃSKI: toponymic nick from the village of Sumin.

S£OMIŃSKI: toponymic nick from the village of Słomin; in rapid speech both sound pretty much the same, hence possible confusion.

ZAB£OCKI: topographic "za błotami" (from beyond the mud flats) or toponymic form the village of Zabłocie (Overmud).

CIEZEWSKI/CIEŻEWSKI: No such names in Poland; maybe it was Ciżewski? That would come from the village of Czyżewo pronounced by some Ciżewo.

Suminska/Slominski sounds rather typical Polish, although it's still possible that your grandmother have a Jewish ancestry. However from these surnames is hard to conclude that. I haven't found them in the list of Jewish surnames here:

genealogy.familyeducation.com/browse/origin/jewish?page=16

@kujawa4sure, you might like to look here at a list of surnames of Jewish people in the Bialystok region. The list includes Slominski.
jri-poland.org/surnames/bialysto.htm

How common was it for Polish Jews to convert to Catholicism just to save their lives, or the lives of their families?

Extremely rare except for people trying to survive during the last war. Most converts did so because they wanted to, perhaps to change their social status or simply because of religious belief. Anglicanism was a popular choice, especially in Warsaw and Bialystok - it was seen as being free of anti-Semitic rhetoric.

Anglicanism? if it exisited in even the most miniscule form anywhere in Poland, it was super marginal, jultra-anecdotal and hyper-peripheral, countable on the fingers of one hand. What Pole would want to have anything to do with a religion concocted by a serial wife-killer?!

I'd be interested to learn more about Anglicanism in the latter city. There's no congregation to speak of now, as far as I know anyway.

Quite popular before the war in Bialystok, especially among Jewish people who converted.


Or for that matter with one led in the same period by a pope who married his own niece and another who poisoned his son.

That's veering off topic though. It is however relevant to the OP that people did convert and for various personal reasons..