SRI of sand

That totally depends on the composition of the sand. You'd have to have it measured or find a vendor or manufacturer that has an SRI value for sand you could use.

In terms of the application of the material, the SRI requirements for SSc7.1 only apply to hardscape, and on the one hand I suppose sand would/could be considered "inanimate" but on the other hand, it is not like the examples offered in the definition, which are "pavement, roadways, stone walls, concrete paths and sidewalks, and concrete, brick, and tile patios." I would think unless it's used on a "roadway" it would be considered permeable surface rather than hardscape.

Anyone have an alternate judgement on sand as hardscape?

There is a CIR that rules aggregates and chat are considered hardscape (So I guess "inanimate" takes precedent in the definition). This is also from the ruling:

Aggregate may be tested using ASTM E1918-06 (Solar Reflectance) and ASTM E408-71(2008) (Thermal Emittance) and then the SRI may be calculated using ASTM E1980. Applicable internationally.
Best,
Andy

Here is the 2011 LEED Interpretation ID that Andy is mentioning above: LI ID #10113 - http://www.usgbc.org/leed-interpretations?keys=10113.

Also, I advised a project in 2013 that did not earn SSc7.1 due to crusher fines and gravel paths. The review comment stated: "However, the narrative states that areas and pathways within the LEED Project Boundary that are crusher fines and gravel have not been included in the calculations. Note that crusher fines and gravel areas are nonroof hardscape surfaces and should not be excluded from the calculations. The documentation does not demonstrate credit compliance."