Patent Publication Number: US-2023133639-A1

Title: Processed slabs, and systems and methods related thereto

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This is a continuation application of U.S. patent application Ser. No. 17/217,351, filed Mar. 30, 2021, which is a continuation of U.S. patent application Ser. No. 17/018,755, filed Sep. 11, 2020 (now U.S. Pat. No. 10,981,293), which is a continuation application of U.S. patent application Ser. No. 16/360,628, filed Mar. 21, 2019 (now U.S. Pat. No. 10,773,418), which is a continuation of U.S. patent application Ser. No. 15/044,599, filed Feb. 16, 2016 (now U.S. Pat. No. 10,252,440), which is a divisional application of U.S. patent application Ser. No. 15/042,881, filed on Feb. 12, 2016 (now U.S. Pat. No. 10,195,762), which is a continuation of U.S. patent application Ser. No. 14/610,172, filed on Jan. 30, 2015 (now U.S. Pat. No. 9,289,923), the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This document describes systems and processes for forming synthetic mold slab products, for example, a synthetic mold slab that is thermoformed or otherwise compacted to a selected slab shape from a mixture including particulate mineral material, resin binder, and pigments so that the synthetic molded slab is suitable for use in living or working spaces (e.g., along a countertop, table, floor, or the like). 
     BACKGROUND 
     Quarried stone slabs are a commonly used building material. Granite, marble, soapstone, and other quarried stones are often selected for use as countertops due to their aesthetic properties. Despite the visual appeal of quarried stone, quarried stones can be quite expensive to obtain and are generally limited to naturally occurring color schemes. 
     Engineered stone slabs may be formed from a man-made combination of materials that can provide improved stain-resistant or heat-resistant properties compared to quarried stone. Engineered stone is typically a combination of particulate mineral material and binder, such as a polymer resin or cement. Some engineered stones partly emulate some aesthetic properties of quarried stone, but still fall noticeably short of the complicated look and texture of quarried stone. 
     SUMMARY 
     Some embodiments described herein include systems and processes for forming synthetic molded slabs suitable for use in living or working spaces (e.g., along a countertop, table, floor, or the like). In particular embodiments, the synthetic molded slabs can be manufactured using, for example, a set of stencils that separate differently pigmented particulate mineral mixes into predetermined regions of a series of molds, thereby providing molded slabs having a similar appearance to one another (which, unlike quarried stone slabs taken from a quarry, can be generally repeatable and predefined as part of the manufacturing process). As used herein, “differently pigmented” means having different pigment combinations or otherwise having a different visual apparent in color tone or visual texture. In such embodiments, however, the appearance of each synthetic molded slab can provide the complex striations and veining patterns that emulate a quarried stone slab. For example, each slab can be formed from a combination of differently pigmented particulate mineral mixes that are separately dispensed into two or more partial molds which combine to facilitate the selected striations and veining patterns. The slabs may be subsequently processed by compression molding and curing operations. 
     Particular embodiments described herein include a process of forming a synthetic molded slab from different particulate mineral mixes. The process may include sequentially dispensing at least first and second pigmented particulate mineral mixes comprising predominantly a quartz material into a single slab mold using at least first and second distributors. The first distributor may output the first pigmented particulate mineral mix through a first stencil positioned over the slab mold and into the slab mold according to a first stencil pattern, and the second distributor may subsequently output the second pigmented particulate mineral mix through a second stencil positioned over the slab mold and into the slab mold according to a second stencil pattern such that the second pigmented particulate mineral mix is deposited in regions of the slab mold that are unoccupied by the first pigmented particulate mineral mix. The process may further include vibrating and/or compacting the pigmented particulate mineral mixes arranged in the slab mold so as to form a synthetic molded slab that is generally rectangular and has major surface. In various embodiments, the major surface may have a width or at least 3 feet and a length of at least 6 feet. Optionally, the aforementioned vibrating and compacting of the pigmented particulate mineral mixes arranged in the slab mold may be performed contemporaneously. Additional embodiments described herein include a synthetic molded slab formed according to this particular process. 
     Some embodiments described herein include a process of forming a synthetic molded slab from a set of different particulate mineral mixes that each include a quartz material, one or more pigments, and one or more resin binders. The process may include outputting a first particulate mineral mix of the set of different particulate mineral mixes from a first distributor and through a first stencil that is positioned over a slab mold and that defines a first pattern of first design apertures surrounded by first occluded regions. The process may further include depositing the first particulate mineral mix passing through the first design apertures into the slab mold so as to partly fill a mold space of the slab mold that is at least 6 feet long by at least 3 feet wide. The process may also include moving the partly filled slab mold relative to the first stencil so that a second stencil is positioned over the partly filled slab mold, and the second stencil may define a second pattern of second design apertures surrounded by second occluded regions. The process may further include outputting a second particulate mineral mix of the set of different particulate mineral mixes from a second distributor and through the second design apertures of the second stencil. Also, the process may include depositing the second particulate mineral mix passing through the second design apertures into the slab mold and into regions of the mold space of the slab mold that are unoccupied by the first pigmented particulate mineral mix. Further, the process may include vibrating and compacting (which are optionally performed contemporaneously) the pigmented particulate mineral mixes arranged in the slab mold so as to form a synthetic molded slab that is generally rectangular and has major surface with a width or at least 3 feet and a length of at least 6 feet. Additional embodiments described herein include a synthetic molded slab formed according to this particular process. 
     In one aspect of this process, the first particulate mineral mix and the second particulate mineral mix may comprise at least two differently colored mineral mixes that each include the quartz material, one or more pigments, and at least one binder. In second aspect of this process, the depositing of the first particulate mineral mix may include distributing the first particulate mineral mix according to a first predefined pattern, and the depositing the second particulate mineral mix may include distributing the second particulate mineral mix according to a second predefined pattern. In a third aspect of this process, the first predefined pattern may define a first pigmented vein, and the second predefined pattern may define a second pigmented vein of the slab. In a fourth aspect of this process, at least a portion of the first pigmented vein may surround at least a portion of the second pigmented vein. In a fifth aspect, the process may further include polishing the major surface of the slab. In a sixth aspect, the process provides the slab in a manner that emulates the appearance of a quarried stone slab due at least in part to the two differently colored mineral mixes distributed according to the first predefined pattern and the second predefined pattern. In a seventh aspect of this process, the depositing the first particulate mineral mix may include depositing the first particulate mineral mix into the slab mold according to a first predefined and repeatable pattern, and the depositing the second particulate mineral mix may include depositing the second particulate mineral mix into the slab mold according to a second predefined and repeatable pattern so as to define complementary regions of multiple different particulate mineral mixes. 
     Further embodiments described herein include a system for forming a synthetic molded slab using a combination of different particulate mineral mixes. The system may include at least one slab mold defining a mold space that is at least 6 feet long by at least 3 feet wide. Also, the system may include two or more stencils defining complementary patterns of open spaces and occluded spaces, and the cumulative areas of the open spaces of the stencils corresponding to substantially the mold space of the particular slab mold. The system may further include two or more mineral aggregate distributors that are each configured to dispense a corresponding particulate mineral mix into the slab mold through a corresponding one of the stencils. Each stencil may be configured to prevent a mix in the distributor from accessing selected areas of each mold in the series of molds. 
     Some embodiments described herein include a set of separately molded synthetic slabs having a substantially repeated rectangular major surface appearance defined by a set of particulate mineral mixes. Each respective slab of the set may include at least two different particulate mineral mixes distributed according to at least two predefined stencil patterns for each of the synthetic slabs in the set of separately molded synthetic slabs. A first mix of the at least two different particulate mineral mixes occupies a full thickness each respective slab at first regions in which a second mix of the at least two different particulate mineral mixes is absent, and the second mix of the at least two different particulate mineral mixes occupies the full thickness of each respective slab at second regions in which the first mix of the at least two different particulate mineral mixes is absent. Optionally, the at least two different particulate mineral mixes may each comprise a quartz material, one or more pigments, and one or more resin binders. Also, each respective slab is rectangular and has major surface with a width or at least 3 feet and a length of at least 6 feet. 
     Particular embodiments described herein include a synthetic molded slab that optionally comprises at least a quartz material. The synthetic molded slab may include a major surface defined by a set of particulate mineral mixes and having a rectangular shape that is at least 2 feet wide by at least 6 feet long and extending perpendicularly to a slab thickness. The major surface may have at least a first pigmented vein pattern defined by a first stencil pattern and a second pigmented vein pattern defined by a second stencil pattern that is a negative of the first stencil pattern. The first pigmented vein pattern may include a first particulate mineral mix that occupies the slab thickness at a set of first regions that collectively provide the first pigmented vein pattern, and the second pigmented vein pattern may include a second particulate mineral mixes that occupies the slab thickness at a set of second regions that collectively provide the second pigmented vein pattern. The first particulate mineral mix may be absent from the set of second regions, and the second particulate mineral mix may be absent from the set of first regions. The first and second particulate mineral mixes may be differently pigmented, and each of the particulate mineral mixes may optionally comprise the quartz material, one or more pigments, and one or more binders. 
     The systems and techniques described here may provide one or more of the following advantages. First, a system can be used to produce a plurality of synthetic molded slabs that each have similar striations and veining patterns and that are suitable for use in living or working spaces (e.g., along a countertop, table, floor, or the like). Such slabs can be formed from a combination of differently pigmented particulate mineral mixes that are vertically distributed into designated regions of each mold according to predefined and complementary dispensation patterns (e.g., two or more horizontally oriented templates that can be positioned over each mold), which provide the selected striations and veining patterns that are generally repeatable for each separately molded slab. 
     Second, each slab in the system can be formed from a compression molding operation in which the molds containing the particulate mineral mixes are maintained in a horizontal orientation after the mold is filled. For example, the differently pigmented particulate mineral mixes are vertically poured through a series of complementary, horizontally oriented templates, the filled mold is shifted horizontally for a subsequent compression molding operation (e.g., vibro-compaction molding, curing, etc.). From there, some or all of the mold is removed from the hardened slab so that at least a major surface of the slab is polished to provide an appearance of the complex striations and veining patterns that emulate a quarried stone slab. In such circumstances, the polished major surface of each of the synthetic molded slabs provides an outer appearance that is remarkably similar to the other slabs in the set of separately molded slabs, unlike quarried stone slabs taken from a quarry. Moreover, the pigments and particulate mineral mixes can be selected to provide color combinations and visual effects that improved upon and offer a variety of color combination options far beyond what is available from quarried stone slabs taken from a quarry. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view of a synthetic molded slab after formation, in accordance with some embodiments. 
         FIGS.  2 A and  2 B  are exploded and assembled views of an example of a first partial slab stencil aligned with a slab mold, in accordance with some embodiments. 
         FIGS.  3 A and  3 B  are exploded and assembled views of an example of a second partial slab stencil that is complementary to the first partial slab stencil of  FIGS.  2 A and  2 B , the second partial slab stencil being aligned with the slab mold of  FIGS.  2 A and  2 B . 
         FIG.  4    is a diagram of an example system for forming a synthetic molded slab product. 
         FIGS.  5 A- 5 D  are diagrams of a synthetic molded slab during and after filling of two partial slab stencils. 
         FIG.  6    is a perspective view of an example synthetic molded slab product formed by the system of  FIG.  4   . 
         FIG.  7    is a flow diagram of an example process for forming a synthetic molded slab product. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG.  1   , a system can be used to produce one or more synthetic molded slabs  50  having a number of striations or veins according to a predefined pattern. Each slab  50  can comprise a quartz material and/or other particulate mineral material that, when mixed with pigments and a resin binder and compressed, provides a hardened slab product suitable for use in living or working spaces (e.g., along a countertop, table, floor, or the like). As shown in FIG.  1 , each slab  50  can be formed from a combination of differently pigmented particulate mineral mixes that are vertically poured into different, designated regions of a respective mold (while the mold is horizontally oriented in this embodiment). These designated regions are repeated for each mold in a series of molds (described in more detail below) due to, for example, a set of stencil structures that can be positioned over each mold and that provide a predefined complementary and repeatable dispensation pattern for the differently pigmented particulate mineral mixes in each mold. In some embodiments described herein, the predefined complementary and repeatable dispensation pattern for the differently pigmented particulate mineral mixes provides the selected striations and veining patterns that are generally repeatable for each separately molded slab. As will be discussed in further detail in the descriptions of  FIGS.  2 A- 7   , some embodiments described herein employ a first partial stencil is arranged above a horizontal slab mold, and a first pigmented particulate mix is dispensed though open portions of the stencil into the mold. One or more successive stencils (e.g., at least a second partial stencil) are positioned over the same mold that is partially filled with the first pigmented particulate mix in predefined regions, and one or more differently pigmented particulate mixes (e.g., at least a second pigmented particulate mix) are sequentially dispensed through open portions of the successive stencils into the mold until all regions of the mold are filled. The mold may be subsequently transported in the horizontal orientation for compaction, curing, and other operations. 
     As shown in  FIG.  1   , depending upon the predefined dispensation pattern of the complementary partial stencils, the dispensation process can provide an aesthetic effect that emulates the veined appearance of natural quarried stone slabs such as granite or marble, including some veins  51  and  52  that extend partly or fully across a complete length L of the hardened slab  50  (e.g., at least 3 feet wide by at least 6 feet long, and between about 3 feet and 6 feet wide and between about 6 feet and 12 feet long, between about 4.5 feet and 5.5 feet wide and between about 10 feet and 11 feet long, and preferably a size selected from one of about 4.5 feet wide by about 10 feet long or about 5.5 feet wide by about 11 feet long). Not only can such differently pigmented veins  51  and  52  extend across the full length of the slab product, but such veins  51  and  52  can also extend through the thickness of the slab  50  (thereby providing a natural vein appearance even when the slab is cut and edged to specific shapes in living or working spaces (e.g., along a countertop, table, floor, or the like). Because each slab  50  in the set of separately molded slabs can include the layers of different particulate mineral mixes dispensed into the mold according to the predefined and repeatable dispensation patterns of complementary stencils, multiple slabs  50  in the set of separately molded slabs can have substantially the same appearance to one another. 
     In this embodiment depicted in  FIG.  1   , the slab  50  comprises two different particulate mineral mixes that are separately dispensed into the mold  130  through two complementary stencils (e.g., a first stencil that is essentially a negative of a second stencil). However, in some embodiments, three or more stencils may be used to repeatably pattern the distribution of three or more different particulate mineral mixes that are separately dispensed into the mold  130 . The different mixes dispensed into each mold according to the repeatable pattern can be compaction molded and cured in the mold (described in more detail below) so as to provide the hardened slab  50  of composite stone material. One or more of the mixes that are used to form the composite stone material can include organic polymer(s) and inorganic (mineral) particulate component. The inorganic (mineral) particulate component may include such components as silicon, basalt, glass, diamond, rocks, pebbles, shells, a variety of quartz containing materials, such as, for example, but not limited to: crushed quartz, sand, quartz particles, and the like, or any combination thereof. In this embodiment, all of the different particulate mineral mixes each comprise a quartz material as a predominant component, which may include sand of various particle sizes and of different combinations. In the hardened slab  50 , the organic and inorganic materials can be linked using a binder, which may include for example, mono-functional or multifunctional silane molecules, dendrimeric molecules, and the like, that may have the ability to bind the organic and inorganic components of the composite stone mix. The binders may further include a mixture of various components, such as initiators, hardeners, catalysators, binding molecules and bridges, or any combination thereof. Some or all of the mixes dispensed in the mold may include components that are combined in a mixing apparatus (not shown) prior to being conveyed to the mold. The mixing apparatus can be used to blend raw material (such as the quartz material, organic polymers, unsaturated polymers, and the like) at various ratios. For example, some or all of the mixes dispensed in the mold may include about 8-95% quartz aggregates to about 5-15% polymer resins. In addition, various additives, may be added to the raw materials in the mixing apparatus, such additives may include, metallic pieces (e.g., copper flecks or the like), colorants, dyes, pigments, chemical reagents, antimicrobial substances, fungicidal agents, and the like, or any combination thereof. 
     Preferably, the mold at least partially defines a length L and a width W of the hardened slab  50  (because the mold retains the particulate mineral mixes therein throughout the subsequent compaction and curing processes). In some embodiments, the width W of the slab  50  formed in the mold is at least 3 feet, between about 3 feet and 6 feet, and preferably about either 4.5 feet, and the length L of the slab  50  formed in the mold is at least 6 feet, and between about 6 feet and 12 feet, preferably about 10 feet. In some implementations, the mold may be sized to form larger (e.g., “jumbo”) slabs, where the width W of the slab  50  formed in the mold is about 5 feet to about 6 feet (e.g., preferably about 5.5 feet) and the length L of the slab  50  formed in the mold is about 10.5 feet to about 12 feet (e.g., preferably about 11 feet). As such, even though each slab  50  can be relatively large in length L, some or all of the veins  51 ,  52  can nevertheless extend across the full length of the slab  50 . In some embodiments, the thickness T of the slab  50  formed is at least 1 inch, between about 1 inch and 5 inches, and preferably about 3 inches. 
     Referring now to  FIGS.  2 A and  2 B , exploded and assembled views of an example of a first partial slab stencil  200 . Referring to  FIG.  2 A , a slab mold  130  and the partial slab stencil  200  are shown in an exploded and inverted view. The slab mold  130  includes a planar mold floor  132  bounded by a collection of mold walls  131  extending perpendicular from the planar mold floor, defining a generally tray-like shape. 
     The partial slab stencil  200  includes an outer frame  202  having a length and width that approximates that of the slab mold  130 . In some embodiments, the slab mold  130  can be at least 3 feet, between about 3 feet and 5 feet, and preferably about 4 feet, and the length L of the slab  50  formed in the mold is at least 6 feet, and between about 6 feet and 10 feet, preferably about 8 feet. In some implementations, the slab mold may be sized to form larger (e.g., “jumbo”) slabs, where the width W of the slab  50  formed in the mold is at least 5 feet (e.g., about 5.5 ft) and the length L of the slab  50  formed in the mold is at least 10 feet (e.g., about 11 ft). In some embodiments, the slab mold  130  can have a thickness T of at least 1 inch, between about 1 inch and 5 inches, and preferably about 3 inches. 
     The outer frame  202  that supports a collection of occluded regions  204  and defines a collection of design apertures  206 . The outer frame  202  and/or the occluded regions  204  can be formed from metal (e.g., steel, aluminum), plastic, wood, composite (e.g., fiberglass, carbon fiber), rubber, or combinations of these and/or any other appropriate material. In some embodiments, the outer frame  202  and/or the occluded regions  204  can include non-stick materials or coatings that can resist adhesion with the ingredients of particulate mineral mixes. 
     The occluded regions  204  extend beyond the outer frame  202  a distance approximately equal to the thickness T of the slab mold  103 . When the partial slab stencil  200  is assembled with the slab mold  130 , as shown in  FIG.  2 B , the outer frame  202  rests upon the mold walls  131  of the slab mold  130 , and the occluded regions  204  extend substantially through the thickness T of the slab mold  130  to contact the planar mold floor  132 . As will be discussed further in the descriptions of  FIGS.  4 - 7   , when the partial slab stencil  200  is assembled with the slab mold  130 , the design apertures  206  define spaces within the slab mold into which a particulate mineral mix can be dispensed, while the occluded regions  204  prevent the mix from entering. 
     Referring now to  FIGS.  3 A and  3 B , exploded and assembled views of an example of a second partial slab stencil  300 . Referring to  FIG.  3 A , the same slab mold  130  (previously depicted in  FIGS.  2 A and  2 B ) and the second partial slab stencil  300  are shown in an exploded and inverted view. Generally speaking, in this embodiment, the second partial slab stencil  300  is complementary to the first partial slab stencil  200  ( FIGS.  2 A and  2 B ). For example, areas that are occluded in the first partial slab stencil  200  are generally open in the second partial slab stencil  300 , and areas that are open in the first partial slab stencil  200  are generally occluded in the second partial slab stencil  300 . In some embodiments, the first partial slab mold  200  may define a “positive” pattern while the second partial slab stencil  300  defines a “negative” pattern that corresponds inversely to the “positive” pattern. 
     The second partial slab stencil  300  includes an outer frame  302  having a length and width that approximates that of the slab mold  130 . The outer frame  302  that supports a collection of occluded regions  304  and defines a collection of design apertures  306 . The outer frame  302  and/or the occluded regions  304  can be formed from metal (e.g., steel, aluminum), plastic, wood, composite (e.g., fiberglass, carbon fiber), rubber, or combinations of these and/or any other appropriate material. In some embodiments, the outer frame  302  and/or the occluded regions  304  can include non-stick materials or coatings that can resist adhesion with the ingredients of particulate mineral mixes. 
     The occluded regions  304  extend beyond the outer frame  302  a distance approximately equal to the thickness T of the slab mold  103 . When the second partial slab stencil  300  is assembled with the slab mold  130 , as shown in  FIG.  3 B , the outer frame  302  rests upon the mold walls  131  of the slab mold  130 , and the occluded regions  304  extend substantially through the thickness T of the slab mold  130  to contact the planar mold floor  132 . As will be discussed further in the descriptions of  FIGS.  4 - 7   , when the second partial slab stencil  300  is assembled with the slab mold  130 , the design apertures  306  define spaces within the slab mold  130  into which a particulate mineral mix can be dispensed, while the occluded regions  304  prevent the mix from entering. In some embodiments, three or more partial slab stencils with design apertures that cumulatively correspond substantially to the length and width of the slab mold can be used (for sequentially dispensing a corresponding number of differently pigmented particulate mixes). 
     Referring now to  FIG.  4   , in some embodiments, a system  400  for forming a set of synthetic molded slab products (e.g., the slab  50  in  FIG.  1   ) is configured to sequentially dispense differently pigmented particulate mineral mixes through two or more complementary partial slab stencils and into the same horizontally oriented mold, which is then processed using a subsequent compression molding operation (e.g., vibro-compaction molding, curing, etc.). The system  400  in the depicted embodiment includes an input conveyor  410  and an output conveyor  420 . A collection of slab molds  130  are transported on the input conveyor  410 . The slab molds  130  provide a form for synthetic molded slab products that are at least three feet wide and at least six feet long. The input conveyor  410  transports the slab molds  130  to an air table  440 . The air table  440  includes a collection of outlets formed on a top surface. Air pumped through the outlets forms a cushion of air between the top surface and the slab molds  130 , to help operators move and/or orient the slab molds  130 . 
     Still referring to  FIG.  4   , the system  400  also includes a collection of mineral aggregate distributors  460   a ,  460   b . In this embodiment, each of the distributors  460   a ,  406   b  is dedicated to dispensing a corresponding particulate mineral mix (refer to  FIG.  1   ). In this embodiment, the partial slab stencil  200  is temporarily assembled to the slab mold  130 . The slab mold  130  is moved horizontally (e.g., relative to gravity) beneath the distributor  460   a , partly filling the slab mold  130  with a first particulate mineral mix. The partial slab stencil  200  is disassembled from the slab mold  130 , and the partial slab stencil  300  is temporarily assembled to the partly filled slab mold  130 . The slab mold  130  is moved horizontally (e.g., relative to gravity) beneath the distributor  460   b , partly filling the slab mold  130  (e.g., the complementary areas left unfilled by the partial slab stencil  200 ) with a second particulate mineral mix. Additional details of this particular embodiment of the partial slab stencils  200 ,  300  are described further in connection with  FIGS.  5 A- 7   . 
     For example, in this embodiment, the first and second partial slab stencils  200 ,  300  are configured to receive two differently pigmented mineral mixes (comprising mostly a quartz material as described above), so there are two corresponding distributors  460   a ,  406   b . In this embodiment, each of the mineral aggregate distributors  460   a ,  460   b  includes a dispensing head  462 . In use, the dispensing heads  462  each receive a corresponding particulate mineral mix from a different mixer line (not shown), such that each dispenser head  462  is configured to release a different particulate mineral mix (e.g., different pigments, different mineral compositions, different additives, or a combination thereof) compared to the other dispenser heads  462 . Each dispenser head  462  is configured to controllably dispense its supply of corresponding particulate mineral mix through the apertures  206 ,  306  of a corresponding one of the partial slab stencils  200 ,  300 . For example, the dispensing heads  462  are each configured with a shutter or valve apparatus (not shown) that is controllable to regulate the flow of particulate mineral mix from the dispensing head  462  to the slab mold  130 . The dispensing heads  462  are controllable dispense fillers into the slab molds  130  at a substantially repeatable rate. Additional details of this particular embodiment of the dispensing head  462  are described further in connection with  FIGS.  5 A- 6 B . 
     In the illustrated example, two mineral aggregate distributors  460   a ,  406   b  and two partial slab stencils  200 ,  300  are used, although in other examples, the slab may be formed from between 2 and 20 different particulate mineral mixes, and more preferably between 3 and 8 different particulate mineral mixes (thereby providing a system that would include a corresponding number of distributors and partial slab stencils). In some examples, the number of mineral aggregate distributors and partial slab stencils can correspond equally to the number of differently pigmented particulate mineral mixes used to create the hardened slab product. 
     After the slab mold  130  has been sufficiently filled, the partial slab stencil  300  is disassembled from the slab mold  130 . The slab mold  130  (now a filled mold  480 ) is moved on a cushion of air provided by an air table  470 , to an output conveyor  120 . As shown in  FIG.  1   , the successive complementary patterns of different particulate mineral mixes that were dispensed into the mold  130  are generally noticeable in the filled molds  480  and are arranged in the horizontal orientation on the output conveyer  420 . Some or all of these successive complementary patterns of different particulate mineral mixes can form the repeatably patterned veins of the hardened slab (e.g., the slab  50  in  FIG.  1   , the slab  600  in  FIG.  6   , or the like). 
     Optionally, the system  400  may include a secondary dispenser (not shown), which may be positioned so that each filled mold  480  passes under the secondary dispenser. The secondary dispenser can be configured to dispense a material that is used to define one more generally “widthwise” veins. Optionally, these widthwise veins may be thinner and spread further apart than the veins defined by the successive complementary patterns of different particulate mineral mixes. Also, these widthwise veins may be formed from a material having a different pigmentation than the particulate mineral mixes dispensed from the distributors  460   a ,  460   b . In some embodiments, the secondary dispenser may be configured with a shutter or valve apparatus (not shown) that is controllable to regulate the flow of pigmented material, thereby providing a predetermined pattern of the widthwise veins that is repeatable for each of the filled molds  480  pass under the secondary dispenser. In some embodiments, the secondary dispenser can be configured to dispense a pigment powder material (e.g., not mixed with quartz material). In other embodiments, the secondary dispenser can be configured to dispense a particulate mineral mix (including a quartz material) having pigments that are different from the mixes dispensed from the distributors  460   a ,  460   b . In some embodiments, the pigment powder material (or other material) dispensed from the secondary dispenser can be deposited along a major (exposed) side of the filled mold  480  so that at least a portion of the material penetrates at least slightly into the thickness of the mineral mix material previously poured into the mold  480  (thereby permitting the widthwise veins to remain viewable even after compaction and polishing of the slab). In such circumstances, the widthwise veins may not extend through the full thickness of the hardened slab (which is different from some or all of the veins defined by the successive complementary patterns of different particulate mineral mixes poured into the mold  130  by the distributors  460   a ,  460   b ). 
     Still referring to  FIG.  4   , the output conveyor  420  can be configured to transport each of the filled molds  480  to one or more sequent stations in the system  400  for forming the hardened slab. For example, each of the filled molds  480  can continue to a subsequent station in which a top mold attachment  494  is positioned over the filled mold  480  so as to encase the layers of particular mineral mixes between the mold  130  and a top cover mold piece (not shown in  FIG.  4   ). From there, the filled mold  480  (now including the top cover mold piece continues to a subsequent station in which a vibro-compaction press  495  applies compaction pressure, vibration, and vacuum to the contents inside the filled mold  480 , thereby converting the particulate mixes into a rigid slab. After the vibro-compaction operation, the filled mold  480  (with the compacted and hardened slab therein) proceeds to a curing station  496  in which the material used to form the slab (including any resin binder material) are cured via a heating process, thereby further strengthening the slab inside the filled mold  480 . After the slab is fully cured (and cooled), the primary mold  130  and the top mold cover piece are removed from the hardened and cured slab at a mold removal station  497 . The primary mold  130  is then returned to the input conveyor  410 . Then, the hardened and cured slab is moved to a polisher station  498 , in which a major surface of the slab is polished to a smooth finish, thereby an appearance of the complex striations and veining patterns that emulate a quarried stone slab. In such circumstances, the polished major surface of each of the synthetic molded slabs provides an outer appearance that is generally repeatable for to the other slabs (from the other filled molds  480  in  FIG.  4   ). 
     Now referring to  FIG.  5 A , the slab mold  130  is shown with the partial slab stencil  200 . The slab mold  130  is partly filled by drawing the distributor  460   a  laterally across the partial slab stencil  200 , or by passing the partial slab stencil and the slab mold  130  laterally beneath the distributor  460   a . The distributor  460   a  holds a first particulate mineral mix, which is controllably released though the dispensing head  462  into the slab mold  130 . The collection of occluded regions  204  block the dispensation of the mix into predetermined areas of the slab mold  130 , while the collection of apertures  206  allow the mix to fill predetermined areas of the slab mold  130 , shown as a collection of filled regions  502 . 
     Referring now to  FIG.  5 B , the slab mold  130  is shown with the partial slab stencil  200  removed after being partly filled according to the pattern provided by the partial slab stencil  200 . As a result, the slab mold  130  is partly filled with the first particulate mineral mix in the filled regions  502 , and is partly unfilled in a collection of unfilled areas  504 . 
     Now referring to  FIG.  5 C , the slab mold  130  is shown with the partial slab stencil  300 . The collection of occluded regions  304  substantially correspond to the collection of filled regions  502  (not visible in this view) and substantially prevent the second mix from being dispensed as a second layer upon the first mix already in the filled regions  502 . Conversely, the collection of apertures  302  substantially correspond to the collection of unfilled areas  504  left by the partial slab stencil  200 . For example the partial slab stencil  300  has a pattern that is the negative of the pattern of the partial slab stencil  200 , and the collective combination of the apertures  202  and  302  substantially correspond to the area (e.g., length L and width W) of the slab mold  130 . 
     The slab mold  130  is partly filled by drawing the distributor  460   b  laterally across the partial slab stencil  300 , or by passing the partial slab stencil and the slab mold  130  laterally beneath the distributor  460   b . The distributor  460   b  holds a second particulate mineral mix, which is controllably released though the dispensing head  462  into the slab mold  130 . The collection of occluded regions  304  block the dispensation of the mix into predetermined areas of the slab mold  130 , while the collection of apertures  306  allow the mix to fill the unfilled areas  504  of the slab mold  130 , shown as a collection of filled regions  506 . 
     Referring now to  FIG.  5 D , the slab mold  130  is shown with the partial slab stencil  300  removed after being partly filled according to the pattern provided by the partial slab stencil  300 . As a result, the slab mold  130  is partly filled with the first particulate mineral mix in the filled regions  502 , and is partly filled with the second particulate mineral mix in the filled regions  506 . 
     In some embodiments, three or more partial slab stencils, distributors, and particulate mineral mixes can be used. For example, four partial slab stencils can be used in which each partial slab stencil has a predetermined pattern of apertures that do not overlap those of the other stencils, and collectively combine to substantially correspond to the area of the slab mold  130 . Four different particulate mineral mixes (e.g., with different aesthetic qualities) can be dispensed into the four collections of apertures to create a four-color composite slab with a pattern that can be substantially repeated for multiple slabs. 
     Referring now to  FIG.  6   , an example synthetic molded slab product  600  can be formed by the system of  FIG.  4    using a combination of differently pigmented particulate mineral mixes that are distributed according to predefined patterns of the two (or more) complementary partial slab templates  200  and  300  into the mold  130 . In some embodiments, the synthetic molded slab product  600  can provide a veined appearance that emulates quarried stone slabs such as granite or marble, depending upon the predefined dispensation pattern of the different particular mixes. For example, the major surface  612  of the slab  600  can be polished and provide at least some veins  602 ,  606  that extend partly or fully across a length and/or width of the hardened slab  600 . Not only can such differently pigmented veins ( 602  and  606 , for example) extend across the slab product, but such veins can also extend through the thickness  610  of the slab  600  from the first major face  612  to the opposing major face  614  (thereby providing a natural vein appearance even when the slab is cut and edged to specific shapes in living or working spaces (e.g., along a countertop, table, floor, or the like). Optionally, at least the major surface  612  of the slab  600  may include a plurality of secondary veins (not shown) defined, for example, by a secondary dispenser. Some of these “secondary” veins can extend fully across a complete width of the hardened slab  600 . Because each slab  600  in the set of separately molded slabs (refer, for example, to the system in  FIG.  4   ) can include the regions of different particulate mineral mixes dispensed into the mold  130  according to the predefined and repeatable dispensation patterns of the partial slab stencils, multiple slabs  600  in the set can have similarly positioned veins in the major surface and can provide substantially the same appearance to one another. 
     The synthetic molded slab  600  can be cut, milled, machined, or otherwise processed to various shapes and sized (e.g., to provide custom-fit countertop surfaces with optional holes for sinks, faucets, or other amenities). For example, a section  630  is cut away from the synthetic molded slab product  600 . With the veins  602  and  606  extending into the interior  606  and/or across the thickness  610 , cutting and/or processing of the synthetic molded slab product  600  shows the veins  602  and  606  in a manner that emulates the aesthetics of cut quarried stone slabs. 
       FIG.  7    is a flow diagram of an example process  700  for forming a synthetic molded slab product (such as slab  50  or  600  described above). In some implementations, the system  400  of  FIG.  4    can be used to perform the process  700 . The process  700  may include the operation  702  of positioning a positive partial slab stencil in a slab mold. In such an operation, a partial slab stencil, such as the partial slab stencil  200  may be temporarily assembled to the slab mold  130 . The process  700  may also include the operation  704  of dispensing a first particulate mineral mix through the positive stencil into the slab mold. For example, as previously described, a first pigmented mix comprising predominantly a quartz material (e.g., a mix including the particulate quartz material, one or more pigments, and one or more resin binders) can be fed into the slab mold  130  using the distributor  460   a  ( FIG.  4   ). Next, the process  700  may include the operation  706  of removing the positive partial slab stencil, and may include the operation  708  of positioning a negative partial slab stencil in a slab mold. In such operations, the partial slab stencil  200  may be removed, and the partial slab stencil  300  may be temporarily assembled to the slab mold  130 . 
     The process  700  may also include the operation  710  of dispensing a second particulate mineral mix through the negative stencil into the slab mold. For example, as previously described, a second pigmented mix comprising predominantly a quartz material (e.g., a mix including the particulate quartz material, one or more pigments, and one or more resin binders) can be fed into the slab mold  130  using the distributor  460   b  ( FIG.  4   ). Next, the process  700  may include the operation  712  of removing the positive partial slab stencil. For example, the partial slab stencil  300  can be removed from the slab mold  130 . 
     The process  700  may further include the operation  714  of contemporaneously vibrating and compacting the particulate mineral mixes arranged in the mold while the mold is in the horizontal orientation. In such circumstances, the operation  714  may provide a compacted slab of composite stone material. Also, in some embodiments, the process  700  may further include the operation  716  of curing the compacted slab. The process  700  may also include the operation  718  of polishing a major surface of the slab to provide a veined appearance on the polished surface of the slab, including but not limited to the examples described above. 
     Although a number of implementations have been described in detail above, other modifications are possible. For example, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. In addition, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.