See Pirkei Avos- how does a sieve retain the fine flour? for background to this question, reproduced here.
אַרְבַּע מִדּוֹת בְּיוֹשְׁבִים לִפְנֵי חֲכָמִים. סְפוֹג, וּמַשְׁפֵּךְ, מְשַׁמֶּרֶת, וְנָפָה. כו' מְשַׁמֶּרֶת, שֶׁמּוֹצִיאָה אֶת הַיַּיִן וְקוֹלֶטֶת אֶת הַשְּׁמָרִים. וְנָפָה, שֶׁמּוֹצִיאָה אֶת הַקֶּמַח וְקוֹלֶטֶת אֶת הַסֹּלֶת
There are four types among those who sit before the sages: a sponge, a funnel, a strainer and a sieve.... A strainer, which lets out the wine and retains the lees; A sieve, which lets out the kemach and retains the choice flour (סֹּלֶת).
The Rav explains that, unlike the "strainer":
The sieve: After we take out the bran and the bruised grain from the ground flour, the [inferior powdery] flour is left with the coarse fine flour, and [the latter] is the [more] important one; we pass it through a very fine sieve. And all of the [powdery] flour - which is like white dust - falls from it, and the coarse important flour remains. And so would they do with grain offerings.
So [too], there is one who has the ability to separate and to cleanse his teachings and take the truth from the false and wasteful.
You see that the "סולת" required for all the menachos (grain-offerings) in the Torah is the coarse flour. The powdery dust is what you sift out.
We see the same in the mishnah in Menachos, 9(2):
כֵּיצַד הוּא בוֹדֵק. הַגִּזְבָּר מַכְנִיס אֶת יָדוֹ לְתוֹכָהּ. עָלָה בָהּ אָבָק, פְּסוּלָה, עַד שֶׁיְּנִיפֶנָּה
How does the Temple treasurer inspect the flour to determine whether it is of sufficiently high quality? The treasurer inserts his hand into the flour. If, when he removes his hand, flour powder ("dust") covers it, the flour is unfit, until one sifts it with a fine sifter, so that no powder will remain.
Any bakers who could explain this? Do we have this today, "coarse fine flour" and worthless "powdery flour"? Where the "fine flour" wouldn't stick to your hand if you stuck it in? It doesn't seem to fit with my impression of the bags of flour my wife brings home.