Hi, Shigawire, looks nice, I've battled with sparkles a bit and, if you don't mind, I'll add a few tips that I've found to be very effective for glittering up some snow...
You might find it more intuitive to keep the specular 'Reflectivity' value at '1' and use a higher 'Index Of Refraction' value, higher than the regular '1.5' in a Default Shader. Maybe 2 to 3, use small increments. That'll should give an outstanding highlight.
You'll however notice the band of sparkles to be very tight and only appearing near the direct light source of the Sun, you can loosen that up and spread it faaaaaaar and wiiiiiide across your surface by increasing 'Specular Roughness'. I've never went higher than a value of '1' for roughness since small increments here can also make a big difference in highlight spread. The slider limit is '0.8' but you can input higher values manually into the text field.
It's likely you'll now see an entirely glossy surface, visit the sparkle fractal's Colour tab and, if 'High Colour' is checked, reduce 'Colour Offset'(if Low Colour is checked, raise offset), to reduce your sparkles back down to little pin-pricks of light again.
To me, after a ton of experimentation, along with lots of tips and contribution with others here on this, among many other subjects on managing reflectivity, it really makes for a much more versatile, and easier to control, spread of highlights, from a tight band, to a full-screen scattering across the entire frame.
