I believe this habit [
www.mindat.org] is closest to the type-description:
"nickeltalmessite Ca2Ni(AsO4)2*2H2O has been found in association with annabergite, nickelaustinite, pecoraite, calcite and a mineral of the chromite-manganochromite series on a dump of the Ait Ahmane mine (Bou Azzer district, Marocco). The new mineral forms botryoidal aggregates consisting of split individuals up to 10 *10 * 20 mkm in size. Color is apple-green, streak white." ( [
rruff.info] )
[
www.mindat.org] this picture might actually show Ni-bearing Talmessite. It would be interesting to know if it has been analyzed.
Lefteris.