Watershed Materials - Technology for New Concrete Blocks
The block with a smaller carbon footprint.

Syar Slate Watershed Block - ASTM C90 Compliant

A single origin mix design, the Syar Slate Watershed Block highlights dark Jurassic basalt from the Syar quarry in Solano County. ASTM C90 compliant.

Syar Slate Watershed Block™

ASTM C90 Compliant - Produced in Napa, California

The Syar Slate Watershed Block is a single origin design that highlights the midnight pitched Jurassic basalt from the Syar quarry in Solano County’s Sky Valley. Rather than reply on the expensive artificial colorants used in ordinary concrete block, Watershed Materials celebrates the geologic origin and natural palette of minerals carefully selected in our mix designs. 

Watershed Materials’ high compression manufacturing process lithifies the mineral grains into a new piece of stone in much the same way that nature turns sediments into rock under very high geologic pressure. The block’s stunning visuals are matched by an increased sustainability profile and industry standard performance. The Syar Slate Watershed Block meets or exceeds ASTM C90 specifications, encouraging engineers and architects to specify the block with confidence.

Nominal Dimensions: 4x8x16”, 6x8x16”, 8x8x16”, Bondbeam blocks 6” & 8” high. See detailed actual measurements here.

Dry Density: 125-130 pcf (standard-weight)

Weight: 22.1 lbs per 4” block, 31.4 lbs per 6” block, 44.1 lbs per 8” block

Compressive Strength: Greater than 1,900 psi (ASTM C90 compliant)

Water Absorption: Less than 13 pcf (ASTM C90 compliant)

Linear Shrinkage: Less than 0.065% (ASTM C90 compliant)

Thermal Conductivity: 0.81-0.93 W/m°C

Acoustic Reduction: 40-50 dB (40 cm wall 500Hz)



The Syar Slate Watershed Block offers an improved sustainability profile compared to traditional concrete block.

  • Incorporates locally sourced, unwashed aggregate, reducing water use and diesel emissions from transportation
  • Reduces cement, an expensive and hugely polluting binder responsible for 6% of humanity's CO2 footprint
  • Avoids energy intensive steam curing
  • Increased density provides natural thermal mass that can offset heating and cooling needs

Product Availability

The Syar Slate Watershed Block is produced in Watershed Materials' factory in Northern California using locally sourced materials. In keeping with our commitment to environmental sustainability - and to reduce transportation costs - the Stanford Watershed Block is available within a 250 mile radius of the San Francisco Bay Area. For certain projects outside this radius, Watershed Materials can provide carbon offset credits for extended transportation.

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