Dan Mosier's Report 09/03/2016
The brick is a common building brick made by the Port Costa Brick Company at the yard near Port Costa, Contra Costa County, California. This is based on the physical mineral composition and manufacturing marks seen in the brick. This company operated the yard from 1905 to 1964, when it sold the property to the Homestake Gold Mining Company. The brick made by this company were all made by an extruding brick machine with automatic wire-cutters that sliced the clay block into eight bricks at a time. The wire-cuts were a low-angle type of cut on the faces of the brick. The wet bricks were fired in a continuous gas-fired kiln at a maximum temperature of 1840 degrees F.
The brick in the cemetery furnace match well with known Port Costa brick. They are extruded, wire-cut common brick, measuring 8 1/2 x 4 x 2 1/2 inches, which is on the larger size of the common bricks made by the Port Costa Brick Company. The wire-cut grooves on the faces are short and form a low-angle curve with a velour texture, which are the tears normal to the wire-cut grooves (see PortCostaBrick1). Most of the loose bricks seen were uniform in color, being orange red. One displayed the typical transverse light yellow flash on the sides commonly seen on Port Costa bricks (see PortCostaBrick2). The smooth sides were also indented with stack indentations and some crazing was noted, both characteristic features in Port Costa common bricks. The most diagnostic feature, however, is the interior composition which is composed of about 5% black shale scattered within a coarsely granular orange-red clay body (see PortCostaBrick3). A few rounded white clay specks are also present. Because Port Costa Brick Company made this style of brick throughout most of its operational history, it is not possible to assign a date for the furnace bricks, except to say that it was made sometime between 1905 and 1960.
About 1960, Port Costa Brick Company began perforating some of their bricks with different shaped holes. One brick present among the furnace brick is a Jumbo (round cores) brick, 11 1/2 x 3 1/2 x 3 inches, with a mat-textured surface (see PortCostaBrick4), which is a characteristic texture found on Port Costa bricks. The sides display short random transverse grooves and the faces have short random longitudinal grooves. The Jumbo contains 5 round cores, about an inch in diameter, in a single row on the faces. The color is a uniform orange-red. Jumbo bricks were made by both the Port Costa Brick Company in the early 1960s and later by the Homestake Gold Mining Company until 1971. However, the lack of the curved wire-cuts indicates that this brick may have been made by a different type of machine that was put in place when Homestake took over the plant. So the date for that brick probably ranges from 1964 to 1971. Not certain why there was only one Jumbo brick present at the furnace site and it is not clear how or where it was used in the furnace. It will be interesting to see if there is a change in the bricks used towards the buried base of the furnace to indicate whether or not the exposed bricks are original to the furnace.
For more information about the Port Costa Brick Works, see http://calbricks.netfirms.com/brick.portcosta.html.
Dan Mosier
California Bricks
calbricks.netfirms.com
The brick in the cemetery furnace match well with known Port Costa brick. They are extruded, wire-cut common brick, measuring 8 1/2 x 4 x 2 1/2 inches, which is on the larger size of the common bricks made by the Port Costa Brick Company. The wire-cut grooves on the faces are short and form a low-angle curve with a velour texture, which are the tears normal to the wire-cut grooves (see PortCostaBrick1). Most of the loose bricks seen were uniform in color, being orange red. One displayed the typical transverse light yellow flash on the sides commonly seen on Port Costa bricks (see PortCostaBrick2). The smooth sides were also indented with stack indentations and some crazing was noted, both characteristic features in Port Costa common bricks. The most diagnostic feature, however, is the interior composition which is composed of about 5% black shale scattered within a coarsely granular orange-red clay body (see PortCostaBrick3). A few rounded white clay specks are also present. Because Port Costa Brick Company made this style of brick throughout most of its operational history, it is not possible to assign a date for the furnace bricks, except to say that it was made sometime between 1905 and 1960.
About 1960, Port Costa Brick Company began perforating some of their bricks with different shaped holes. One brick present among the furnace brick is a Jumbo (round cores) brick, 11 1/2 x 3 1/2 x 3 inches, with a mat-textured surface (see PortCostaBrick4), which is a characteristic texture found on Port Costa bricks. The sides display short random transverse grooves and the faces have short random longitudinal grooves. The Jumbo contains 5 round cores, about an inch in diameter, in a single row on the faces. The color is a uniform orange-red. Jumbo bricks were made by both the Port Costa Brick Company in the early 1960s and later by the Homestake Gold Mining Company until 1971. However, the lack of the curved wire-cuts indicates that this brick may have been made by a different type of machine that was put in place when Homestake took over the plant. So the date for that brick probably ranges from 1964 to 1971. Not certain why there was only one Jumbo brick present at the furnace site and it is not clear how or where it was used in the furnace. It will be interesting to see if there is a change in the bricks used towards the buried base of the furnace to indicate whether or not the exposed bricks are original to the furnace.
For more information about the Port Costa Brick Works, see http://calbricks.netfirms.com/brick.portcosta.html.
Dan Mosier
California Bricks
calbricks.netfirms.com